bluuebunny/crossref_metadata_2025 huggingface dataset:
The Ionic Properties of the Capsular Fluid Bathing Embryos of Lymnaea Stagnalis and Biomphalaria Sudanica (Mollusc A: Pulmonata)
Authors: Taylor H. H.
Published: April 2021

The cations sodium, potassium, calcium and magnesium are always at a higher concentration in the capsular fluid (perivitelline fluid) of Lymnaea stagnalis and Biomphalaria sudanica than in the bathing medium. The concentration of each ion is a complex function of the concentrations of all ions in the medium and of pH. Typical values for the ratio of capsular concentration to medium concentration for Lymnaea capsules isolated in slightly alkaline water of average hardness are 2·4–5 for monovalent and 18–40 for divalent cations. Lowering the pH of the medium from 8·5 to 4·0 reduces the capsular concentrations of monovalent ions by about 45% and of divalent ions by about 85%. Consideration of the potential difference between the capsular fluid and the medium, and comparison of the monovalent and divalent ion ratios, indicates that a Donnan equilibrium exists across the capsular membrane. On dilution of the medium the above ratios may rise more than tenfold and the potential difference may rise from about 23 mV to above 60 mV (inside negative). It is concluded that the capsular fluid/membrane system buffers the internal cation activities against changes in external cation activities, particularly in the case of calcium. It is suggested that the ‘calcium-buffer’ may be important in maintaining ion-uptake mechanisms near saturation, in reducing the permeability of the embryo to salts and water, in maintaining cellular adhesion and in morphogenesis. The fluxes of 22Na+ and 45Ca2+ across the capsular membrane have half-times of 40–100 sec and about 300 sec respectively. The membrane offers little resistance to the free diffusion of these ions.
The Effects of Derivatives of Adenosine 3′,5′-Monophosphate on Fluid Secretion by the Salivary Glands of Calliphora
Authors: Berridge M. J.
Published: April 2021

The nature of the cyclic AMP-receptor interaction was analysed by testing a range of cyclic nucleotides on the isolated salivary glands of adult blowflies. All compounds containing modifications in the region of ribose or the phosphate ring were inactive. One compound, adenosine 3′,5′-phosphorothioate, appeared to compete with cyclic AMP. A number of nucleotides with alterations restricted to the base region of the molecule could stimulate secretion equally as well as cyclic AMP. These observations indicate that during the action of cyclic AMP the phosphate ring and ribose sugar are critical whereas the adenine ring plays a relatively unspecific role.
Motor Activity During Walking in the Cockroach Periplaneta Americana
Authors: Delcomyn F. , Usherwood P. N. R.
Published: April 2021

The patterns of electrical activity of selected muscles of the rear legs were studied during locomotion in unrestrained, freely moving cockroaches. During walking, muscle potentials in both extensor and flexor muscles were always grouped into bursts separated by periods of silence, with one burst occurring per step. During very slow walking, the occurrence of flexor and extensor bursts was synchronized with, respectively, the flexion and extension movements of the leg. At increasingly greater speeds of locomotion, the movements of the leg lagged increasingly behind the muscle activity, so that during very fast walking the extensor or flexor burst often began while the preceding leg movement was not quite half completed. ‘Slow’ extensor and’fast’ flexor bursts were studied in detail. The frequency of impulses within each extensor burst was usually steady, but sometimes declined in the middle or increased at the end of a burst. Frequency within’fast’ flexor bursts was often more varied, but there was no systematic change in frequency with any other parameter which was examined. For’slow’ extensor bursts, the duration of each burst, the number of impulses per burst and the mean interval between impulses in a burst each increased significantly as the duration of the associated step increased, i.e., there was a positive correlation between each pair of parameters. The rate at which the number of impulses per burst and mean interval per burst changed as a function of step duration was often significantly higher for steps shorter than about 300 msec than for longer ones. For’fast’ flexor bursts, the duration of each burst, the number of impulses per burst and the mean interval per burst were each extremely variable ; a weak correlation with step duration could only be demonstrated for the latter. However, both mean interval and the number of impulses per burst were positively correlated with the duration of the burst from which they were taken. The data qualitatively support current models of step generation in insects, but also suggest that a useful distinction could be made between very slow walking (below 3–4 steps per sec), termed ambling, and faster walking.
Electrophysiological Identification of Neurones and Neural Networks in the Perioesophageal Ganglion Complex of the Marine Pulmonate Mollusc, Onchidium Verruculatum
Authors: Katayama Yoshifumi
Published: April 2021

The marine pulmonate mollusc, Onchidium verruculatum, has many giant neurones in the perioesophageal ganglion complex. Twenty of them were visually identified by their relative locations, sizes, and pigmentations under the dissecting microscope, and electrophysiologically by their input-output patterns. The relationship among and between the giant neurones was investigated on 190 pairs of neurones, arbitrarily paired from 20 neurones, by intrasomatic recordings. There were two excitatory and two inhibitory direct connexions. There were two pairs receiving synchronous excitatory inputs and two pairs receiving synchronous inhibitory inputs. Two pairs of neurones showed a similar activity pattern and one pair showed an alternating activity pattern. A tentative neural network was constructed for one of identified neurones, r-PP i in the r-PPG (right pleuroparietal ganglion). The results and the firing patterns of neurones are discussed.
Repetitive Firing in Molluscan Giant Neurones
Authors: Magura I. S. , Zamekhovsky I. Z.
Published: April 2021

The repetitive responses of molluscan neurones to steady injected outward current have been examined using intracellular microelectrodes. Voltage-clamp experiments were also performed to investigate the participation of transport mechanisms for potassium current in neurones during firing. The maximum rate of rise of action potentials usually decreases during repetitive firing. Simultaneously an increasing duration of the falling phase of spikes is observed. The peak level of spikes in most cases is relatively stable if external Ca2+ concentration exceeds 3−4 mM. The peak level of action potentials markedly decreases during firing in solutions with low Ca2+ concentration. A similar effect is observed if the Ca2+ ions in normal Ringer solution are completely replaced by Mg2+ ions. With increasing external Ca2+ concentration the maximum rate of rise of action potentials becomes more stable during repetitive firing. With increasing external Ca2+ concentration the steady-state inactivation of fast transient potassium channels is removed. Increase in Ca2+ concentration (in range from 10–40 mM) is roughly equivalent to a hyperpolarization of 7–8 mV. Experiments with TEA show that in some neurones of Limnea stagnalis the last transient potassium channels participate in carrying potassium current during the falling phase of the action potentials at the beginning of repetitive firing. The role of potassium inactivation as well as of Ca2+ ions in mechanisms which stabilize the peak level of action potentials during repetitive firing is discussed.
On the Feeding Mechanism of the Copepods, Calanus Finmarchicus and Diaptomus Gracilis
Authors: Cannon H. Graham
Published: April 2021

Calanus finmarchicus and Diaptomus gracilis both feed automatically when swimming slowly and steadily through the water. A feeding current is produced which is filtered by the stationary maxillae. Food so obtained is passed on to the mandibles by the maxillulary endites and setae on the bases of the maxillipeds. The feeding current is a vortex passing through the mouth parts which results automatically from the swimming activities of the antennae, mandibular palps and maxillules. The feeding vortex is caused to pass through the maxillae by the combined activities of the maxillipeds and the maxillulary exites. The former suck water into the filter chamber between the maxillae while the latter suck it out through the maxillary setae. The views of Storch and Pfisterer on the feeding mechanism of Diaptomus gracilis are criticised. There is no powerful antero-posterior swimming current as described by these authors. The swimming current is in the form of a vortex encircling the body and most marked at the sides in the angle between the body and the antennules.
Observations on Ovulation in the Rabbit
Authors: Walton A. , Hammond J.
Published: April 2021

Ovulation has been directly observed in the anaesthetised rabbit. The follicle ruptures, on the average, about 10 hr. after coitus but there is some variation and all follicles do not rupture simultaneously. Ovulation is not the invariable consequence of the normal growth of the follicles and, although confined to those which are mature, is independent of the actual size attained. Ovulation is accompanied by increased vascularity of the follicle. The principal cause of rupture is the rapid distension of the follicle by marked secretory activity. The ovum is carried out in the flow of this secretion. Ovulation in the rabbit is initiated by some component of the orgasm which accompanies coitus rather than by the mechanical stimulus of the penis or the presence of semen in the vagina. Corpora lutea are not formed if the follicle is ruptured artificially and this effect is not due to operative trauma but to the absence of some effect of coitus necessary for the formation of the luteal tissue. Artificial rupture or ablation of ripe follicles is followed by an immediate compensatory growth of new follicles. Blood follicles formed from those artificially ruptured do not inhibit this compensatory growth.
Intracellular Oxidation-Reduction Studies
Authors: Chambers Robert , Pollack Herbert , Cohen Barnett
Published: April 2021

A New approach to the problems of cellular metabolism was opened by J. and D. Needham (8) who used the micro-injection of reversible indicators to determine the oxidation-reduction intensity of living protoplasm. Prerequisites for this work were the elaboration of a series, as yet incomplete, of such indicators, and the electrometric standardisation of the position of each dye on the scale of reduction (or oxidation) electrode potential by Clark, Cohen and their co-workers (1, 4, 5, 7). Discussions of the various theoretical phases of oxidation-reduction and their possible applications to the study of life processes are found in the papers of Clark and Cohen (5).
Digestion in Ascidians and the Influence of Temperature
Authors: Berrill N. J.
Published: April 2021

The mechanism of feeding and digestion in the Pyurid Ascidians Tethyum pyriforme americanum and Boltenia ovifera is described. The structure and histology of the “liver “is described and it is shown that it is primarily an organ of secretion. It is found that the only digestive enzymes are those poured into the gut by the liver, and consist of a powerful amylase, a protease, a very weak lipase, and also an invertase, a maltase, and a lactase. The brownish pigment of the liver gives reactions with acids somewhat like those of bile pigment. There is no trace of bile salts, however, nor of cholesterol. The amylase has an activity range from pH 6.0 to pH 8.5 with an optimum near pH 7·5. The protease is active from pH 6·0 to above pH 10·0. A similar protease is secreted by Molgula citrina and Ascidia prunum. The relative strengths of the amylase and protease are compared, the amylase being very much the stronger. While experiments of brief duration indicate an optimum temperature for enzyme activity above 40° C., the more prolonged the experiments the lower does the optimum become. Whatever the optimum may be after an experiment of 2 hours’ duration, it falls about 20° C. during the next 45 hours, if the experiments be so prolonged. At 15° C. and at 10° C. the food takes about 35 and 55 hours respectively to pass through the alimentary canal, and at 5° C. somewhere between 70 and 90 hours. These temperatures approximately cover the normal range in temperature of the environment, and therefore of the animal itself. From experiments lasting 33 hours the optimum temperature for enzyme activity was found to be about 17° C. ; that is, within one or two degrees of the body temperature. From experiments lasting 57 hours the optimum temperature was found to be about 13° C.; that is, within three degrees of the body temperature. These temperature optima not only represent the relative amounts of substrate converted at different temperatures, but also represent the absolute amounts converted and convertible. The enzymes, amylase and protease, are two-thirds to three-quarters destroyed during their period of activity within the alimentary canal of the animal, and in order to utilise the remainder the digestion mixture would have to be retained within the canal for twice as long a time. Therefore it seems probable that the organism in making such a compromise between a high activity of the enzyme and its economical use is working to a maximum efficiency ; and it is possible that a permanent increase in the stability of the digestive enzymes would be turned to advantage through a more prolonged retention of the food within the gut.
On the Spherical Form of the Mammalian Erythrocyte
Authors: Ponder Eric
Published: April 2021

In 1895 Hamburger described a remarkable phenomenon which can be observed in suspensions of mammalian red cells in isotonic, hypotonic, or hypertonic saline and in sugar solutions, but not in serum or plasma. The normally biconcave discoidal cells become perfect spheres, without undergoing any apparent alteration in volume; the addition of serum to the suspension of spherical cells, however, converts the spheres back again into the typical discoidal form. Hamburger has no explanation to offer for the occurrence of this phenomenon, but suggests that it may be due to changes in surface tension.

In 1920 Brinkman and van Dam published a study of the phenomenon, in which they record the changes undergone by the red cells of man and of the rabbit when placed in a haemocytometer chamber. They correct Hamburger’s statement in one important respect, for they observe that red cells in saline are not spherical but discoidal, and that they become spherical only when placed in the haemocyto-meter chamber. In becoming spheres they pass through an intermediate form, “the crab-apple form,” which is spherical but finely crenated. Brinkman and van Dam believe that the cause of the phenomenon is that the cells receive an electrostatic charge from the glass when they come into contact with the floor of the chamber. They confirm Hamburger’s statement that the change from disc to sphere is prevented by the presence of serum, and claim that it is the cholesterol contained in the serum which inhibits the change of form.

Unaware of these two investigations, Gough in 1924 described the same phenomenon once gain, but fell into Hamburger’s error of believing that the red cells are spherical when suspended in a volume of saline. This error is very easy to make, and both Millar and I have made it also; indeed, as will be seen below, it is impossible to avoid it if an oil immersion objective is used for examining the cells. Gough adds two interesting observations to the previous descriptions: that ammonium oxalate and ammonium chloride act like serum in preventing the cells from becoming spherical in saline, and that the spherical form becomes crenated after a few hours, passing spontaneously into the discoidal form in about 24 hours. He does not give any detailed explanation of the phenomenon.

Both Millar and myself (Millar 1925, Ponder 1925) made the same mistake as Gough and Hamburger, in believing that the spherical form is due to the immersion of the cells in saline and that cells are spherical when freely suspended in this medium. On such an assumption, I carried out many measurements of sedimentation velocity without receiving any indication that the assumption was wrong1. It appears, however, on a more detailed examination, that the essential condition under which the spherical form occurs has escaped all the observers who have worked on the subject, and that the phenomenon is much more complex than has hitherto been believed.
The Modification of the Cloaca and Teeth of the Adult Salamander, Desmognathus, by Testicular Transplants and by Castration
Authors: Noble G. K. , Pope S. H.
Published: April 2021

In 1926 de Beaumont showed that some of the secondary sexual characters of the male newt, Triturus cristatus, could be produced in the spayed female by testicular transplants. About the same time one of us (Noble, 1926) noted that cloacal glands could be made to arise de novo in the glandless cloaca of the female Desmognathus fuscus fuscus by the same method. Ponse (1923) with young females, and Welti (1925) with adult females, had previously demonstrated that toads which had been experimentally masculinised would develop nuptial pads. The above investigations were of interest in that they demonstrated, in both Caudata and Salientia, that structures not visible even as rudiments in the female could be made to appear and develop under the influence of the male sex gland.
A Method of Estimating the Scatter of Red Cell Populations from Their Diffraction Patterns
Authors: Ponder Eric
Published: April 2021

All the existing methods for determining the diameter of red cells by the observation of the diffraction patterns which they produce are concerned with the determination of mean diameter only, and rest upon expressions which relate the position of the various maxima and minima to the diameter of a number of circular disks of uniform size (Pijper, 1919, 1923, 1925; Millar, 1926; Allen and Ponder, 1928). As is well known, the red cells which produce the diffraction patterns are not of uniform diameter, but it is assumed in the use of these methods that the diameter given by the formulae is the mean diameter of the red cell population.
The Water Balance of A Serpulid Polychaete, Mercierella Enigmatica (Fauvel)
Authors: Skaer Helen Le B.
Published: April 2021

The accessibility of the coelomic and extracellular fluid compartments to the blood and the external bathing medium have been studied in the serpulid polychaete Mercierella enigmatica. Only the single cell layer of the blood-vessel walls separates the blood from the other body fluids. It is likely that this layer is relatively permeable to water and to molecules of low molecular weight so that changes in ion concentration at the surface of tissues, such as the muscles, probably parallel the extensive changes in the blood. Two types of longitudinal muscle fibre, differing in filament diameter, cell shape and distribution have been observed. The pattern of electrical activity recorded by intracellular micro-electrodes falls into two classes, separable on the basis of several parameters. This pattern is discussed in relation to the two types of longitudinal muscle fibre found.
Micromanipulation of the Flagellum of Crithidia Oncopelti
Authors: Holwill M. E. J. , McGregor J. L.
Published: April 2021

The behaviour of the flagellum of Crithidia oncopelti when subjected to constriction and dissection by a microprobe was investigated. Constriction of the flagellar tip resulted in wave reversal, whereas dissection of this region allowed normal wave movement. Constriction of the basal region allowed both base-to-tip and tip-to-base propagation. The observed behaviour is more easily explained in terms of a sliding filament model of flagellar movement than by a model which involves local contraction.
Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris
Authors: Drewes C. D. , Pax R. A.
Published: April 2021

Patterns of innervation of the longitudinal muscle of the earthworm, Lumbricus terrestris, were examined electrophysiologically. The longitudinal musculature of a segment is innervated by relatively few axons, a fast and slow axon being present in segmental nerve I and in the double nerve, segmental nerve II–III. Single-pulse stimulation of the fast axon produces large external muscle potentials and small twitch-like contractions, which with repetitive stimulation are antifacilitating. Repetitive stimulation of the slow axon produces large, slowly developing and sustained mechanical responses, with electrical and mechanical responses showing summation and facilitation. The amplitude and time course of slow mechanical responses are related to the frequency of stimulation. Individual longitudinal muscle fibres are innervated by either the fast or slow axon in a segmental nerve, or by both fast and slow axons. No evidence was found for peripheral inhibitory innervation of the longitudinal muscle.
Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris
Authors: Drewes C. D. , Pax R. A.
Published: April 2021

The motor fields of individual segmental nerves have been mapped electro-physiologically in the longitudinal muscle of the earthworm, Lumbricus terrestris. The anterior pair of segmental nerves (SN I) innervates approximately the anterior two-thirds of its segment and a small portion of the segment just anterior to it. The posterior pair of segmental nerves (SNII-III) innervates approximately the posterior two-thirds of its segment and a small portion of the segment just posterior to it. Adjacent nerves (both intrasegmental and intersegmental) have partially overlapping motor fields; that is, adjacent segmental nerves innervate some of the same longitudinal muscle fibres.
Electrical Potential Differences and Ionic Transport in the Larva of the Mosquito Aedes Aegypti (L.)
Authors: Stobbart R. H.
Published: April 2021

Measurements have been made, in the 4th-instar freshwater larva of the mosquito Aëdes aegypti, of (i) potential differences between haemolymph and medium; (ii) the effects upon sodium fluxes of metabolic inhibitors and of sodium-free solutions. The measurements of potential differences together with those of the Na, Cl, and K concentrations in the larvae show that Na and Cl are actively transported from the medium into the haemolymph, whereas K is probably taken up passively in company with Cl. Using Goldman’s constant-field equation and the present, and earlier, data it can be shown that the expected passive fluxes of Na and Cl between the larvae and the medium are very much smaller than the observed fluxes. KCN and de-ionized water immediately reduced Na outflux to one-sixth to one-seventh of the normal value; KCN also inhibits Na influx more or less completely. The passive Na fluxes through the anal papillae (which cause almost all the ionic movements) appear to be very small. Overall the data show that the influxes and outfluxes of Na and Cl cannot be explained in terms of passive movements. Nor can the increased outflux of these ions which is observed at high external concentrations be explained by Kirschner’s theory of ‘back-transport’. The data, however, are fully compatible with a model for ionic pumps suggested earlier, which would cause both net uptake and exchange of an ion. The data are discussed in terms of a refined version of this model.
Pressure Distribution on the Body Surface of Swimming Fish
Authors: Dubois Arthur B. , Cavagna Giovanni A. , Fox Richard S.
Published: April 2021

Although there are a number of papers on how fish swim (Gray, 1957; Aleev, 1969; Lighthill, 1969), we have been unable to find any measurements of the pressure on the body surface measured while a fish is swimming. A preliminary calculation using the Pitot equation indicated that the pressure against the anterior surface of the fish, expressed in centimetres of water, would be approximately equal to the square of the speed of the fish in miles per hour. A fish one foot long, swimming at six miles per hour, would have a pressure of about 36 cm H2O against the front of his head. Such pressures, if actually present, might be large enough to affect the body functions, particularly circulatory, and ultimately influence the body structure of aquatic animals. They are of the same order of magnitude as the hydrostatic pressures due to gravity acting on land animals of equal body size, and as the blood pressure in fish (Satchell, 1971). In addition, the determination of the pressure distribution on the body surface of swimming fish may be of help in explaining the mechanism of fish locomotion. Compared to pressure distribution on the body surface of dead fish, or casts, the difference may be responsible for the otherwise unexplained ability of some fish to sustain locomotion with relatively little energy expenditure (Gray, 1957; Schmidt-Nielsen, 1972). In this study we measured the pressure on the body surface of swimming bluefish, and we speculate as to the physiological implications of the pressures which were found.
Oxygen—Sensitive Elements in the Book Gills of Limulus Polyphemus
Authors: Crabtree Robert L. , Page Charles H.
Published: April 2021

The unit responses of oxygen-sensitive elements in the book-gill lamellae of Limulus polyphemus were examined by recording their unit activities in the gill nerve while varying the oxygen tension in the sea water bathing the lamellae. Three types of oxygen-sensitive units were detected. Some units (class I) were excited by oxygen introduced into anaerobic sea water; others (class II) were inhibited by high oxygen levels. Some units responded to tactile stimulation only in the presence of oxygen. It is suggested that the oxygen-dependent ventilatory reflexes result from interaction in the central ventilatory neural system of the excitatory effects of class I units and of touch-sensitive oxygen-dependent units with the inhibitory effects of class II units.
Studies on Locust Neuromuscular Physiology in Relation to Glutamic Acid
Authors: Clements A. N. , May Terry E.
Published: April 2021

Two nerve-muscle preparations were used to investigate the physiology of the locust retractor unguis muscle in relation to L-glutamic acid. These were an ‘isolated preparation’, in which the muscle and its nerve were dissected out, and a ‘perfused-femur preparation’, in which the muscle suffered no mechanical disturbance. Exposure of the nerve-muscle preparations to glutamate caused a variety of responses, some of which were shown to be abnormal and due to the experimental conditions. When locust femora were perfused with saline or haemolymph the retractor unguis muscles were much more severely affected by glutamate if the hydrostatic pressure was slightly raised. At raised pressures the perfused-femur preparations were particularly prone to give repetitive and spontaneous contractions. Analysis of haemolymph from adult male locusts showed that it contained, on average, 0·2 mmol/1 L-glutamate, 45 mol/1 total non-peptide amino acids, 5·0 mmol/1 calcium, and 11·6 mmol/1 magnesium. It was calculated that approximately 50% of the calcium and 75% of the magnesium ions are bound to amino acids, and that approximately 25 % of the glutamic acid is bound to divalent metal ions. The isolated preparations were severely affected by glutamate at the concentration at which it occurs in haemolymph, and it was concluded that in the intact locust some mechanism must protect the neuromuscular synapses from haemolymph glutamate. No evidence could be obtained of the sequestration of glutamate by haemocytes, or of binding of glutamate to haemolymph proteins. Calcium and magnesium ions reduced the sensitivity of nerve-muscle preparations to glutamate to a greater extent than could be accounted for by the formation of amino acid-metal complexes. This suggests that the protection afforded by calcium and magnesium involves an interaction of the metal ions with the neuromuscular system itself. The retractor unguis muscle was much less sensitive to glutamate when it was contained within an undissected femur than in an isolated preparation. It was concluded that the muscle is normally protected from haemolymph glutamate by a diffusion barrier which is damaged on dissection. Comparison of the fine structure of retractor unguis muscles, fixed either after dissection or while still contained within the femur, showed that dissection normally caused a partial separation of muscle fibres and damage to the connective tissue sheath, with the resultant exposure of some nerve endings. The connective tissue sheath may constitute the postulated diffusion barrier. The excitatory synapses of the locust retractor unguis muscle are believed to be isolated from haemolymph glutamate by a diffusion barrier, which is tentatively identified with the connective tissue sheath that binds the muscle fibres together. Calcium and magnesium ions reduce the sensitivity of nerve-muscle preparations to glutamate, and may have such a role in the living insect.
Control of Head Movement in the Locust, Schistocerca Gregaria
Authors: Shepheard Peter
Published: April 2021

Head movement in the locust Schistocerca gregaria is mediated by 14 pairs of muscles. The normal motor output to many of these muscles has been investigated in the intact insect by recording with two intracellular microelectrodes from different fibres of a muscle during slow and fast phases of optokinetic nystagmus elicited by rotation of a striped drum in the visual field. In addition, details of the innervation pattern and muscle fibre spectrum of the muscles have been investigated by paired intracellular recording during graded stimulation of the motor nerves in the dissected preparation. Of more than 60 different axons shown histologically to innervate the neck muscles on each side, the activity of about 25 have been analysed and deductions are made about the way the muscles work together in concert to produce head movement. At least four physiologically distinct types of axon innervate several muscles. These types are tonic (slow), phaso-tonic (intermediate), phasic (fast) and inhibitory. Stationary head positions are maintained by low levels of motor output in the tonic axons alone, these axons also being mainly responsible, when active at higher frequency, for producing small slow head movements. Phaso-tonic axons become progressively more active during larger or faster head movements to augment the effect of tonic axon activity. The fastest head movements are correlated especially with activity of the phasic axons. Inhibitory neurones are active during and immediately before rapid head movements, the output to individual muscles being correlated with both contraction and relaxation. On the basis of their electrical responsiveness to the axons innervating them, muscle fibres have been classified into the following types: ‘phasic’, ‘intermediate’ and ‘tonic’, with the tonic class subdivided into ‘ordinary tonic’, ‘super-tonic’ and ‘super-sensitive’. Some muscles contain only a small range of fibre types, while others contain the complete range. Deductions are made about the way the different axon types interact on the different muscle fibre types to elicit various degrees of contraction or tension. The slow phase motor output patterns are the result of a centrally determined programme elicited by visual input (rotation of the striped drum), and are not dependent on, but may perhaps be modified by, proprioceptive feedback. On the other hand, the fast phase of nystagmus is initiated by the central nervous system only after reference to the proprioceptive input from various sense organs of the neck and prothorax.
Net Fluxes of Water in the Isolated Gills of Anguilla Dieffenbachii
Authors: Shuttleworth T. J. , Freeman R. F. H.
Published: April 2021

Measurements of net flux of water have been made on isolated gills removed from freshwater-adapted and seawater-adapted eels and incubated in various media of differing osmotic pressure. From these measurements it has been possible to determine the osmotic permeability coefficient of the gill directly from the net water flux. The values obtained (0 · 50 +0 · 14 × 10−5 cm.sec−1 for freshwater eels and 0 · 43 ± 0 · 07 × 10−6 cm.sec−1 for seawater-adapted eels) indicate that there was no significant change in this parameter on adaptation of the eels to sea water. The direct measurements made of the net water flux across the isolated gills appear to be compatible with the osmoregulatory pattern of eels as deduced by other workers using different techniques. In particular they illustrate and further emphasize the significance of drinking in the freshwater fish. Calculations indicate that, for a freshwater teleost, the osmotic and ionic problems caused by drinking in fresh water have an insignificant energetic effect and hence, energetically, it matters little to the fish whether it drinks or not.
Neuronal Modulation of Photoreceptor Activity in the Bee Moth Galleria Mellonella
Authors: Koopowitz Harold , Stone George
Published: April 2021

Pairs of light stimuli given at varying intervals causes changes in fast-adaptation characteristics in the bee moth Galleria mellonella. With increasing intervals between the stimuli of up to 1·0 sec there is a decrease in the amplitude of the visual response to the second stimulus. This depression of the response can be affected by a variety of agents which alter synaptic activity. Application of compounds such as Mg2* and nicotinic acid, which block synapses, to the optic ganglion lift depression. K+ and CO2 applied to the optic ganglion also abolish adaptation. Severing neuronal connexions between the retina and ganglion also lifts the depression. De-ganglionation and nicotinic acid also result in increases in absolute amplitude of the response. If Ca2+ is added to the Ringer bathing the ganglion, adaptation becomes more marked. These results suggest that the decreases in sensitivity following a brief light stimulus are mediated by synaptic feedback onto the receptor cells.
The Physiology of the Tettigoniid Ear
Authors: Lewis D. B.
Published: April 2021

The effects of blocking the anterior and posterior tympanal slits suggests that the slits are effectively closed to spiracular sound input, but open to tympanal slit inputs. Removal of both the anterior and posterior cuticular folds significantly lowers the threshold curves for both spiracular and tympanal slit entry. The sensitivity to tympanal slit entry is increased to that of the normal spiracle. Destruction of the anterior membrane eliminates all responses in the frequency range 1–20 kHz; removal of the posterior membrane reduces sensitivity. Point-contact vibration of the three membranes at 16 kHz indicates that the central membrane is non-vibratory and that although the posterior membrane is poorly coupled to sound up to 20 kHz, its mechanical movements are transduced with less loss than those of the anterior membrane.
The Physiology of the Tettigoniid Ear
Authors: Lewis D. B.
Published: April 2021

The threshold curve obtained for the whole organ, with a lateral sound source 30 cm from the insect, indicates the degree of interaction that occurs between the spiracular and tympanal slits inputs. The threshold curve for the whole organ with the spiracle blocked shows an increase in threshold to the level of the tympanal slits, and suggests that diffraction phenomena may be important during sound reception. Measurement of the sound intensity emitted by mechanical vibration of the tegmen shows that there is a fall in sound intensity from 124 dB at source to 54 dB at the spiracle; the spiracular intensity is still above the spiracular threshold, however.
The Physiology of the Tettigoniid Ear
Authors: Lewis D. B.
Published: April 2021

The thresholds for the spiracle and for the tympanal slits have been determined at a variety of angles to the body axis and show little directionality. A difference in threshold levels of 20 dB exist between the ipsilateral and contralateral whole organs in the frequency range 1− 20 kHz. Single-frame exposures of a video-tape recording show that the spiracular dimensions do not change during stridulation. In the light of the evidence, a new hypothesis for acoustic orientation behaviour is advanced.
The Editors and the Journal
Authors: Parry D. A.
Published: April 2021

Percipient users of this Journal will note that it is now no longer edited by Sir Vincent Wigglesworth and Professor J. A. Ramsay. Older readers will reflect that such changes of Editorship have been rare events: in fact, if we set aside the brief original Editorship of Professor Crew (1923–5), this is only the second editorial turn-over in the Journal’s 50 years. We hope that the new Editor, Dr J. E. Treherne, and his associates, will regard this as a good omen.
Aestivation of the African Lungfish Protopterus Aethiopicus: Cardiovascular and Respiratory Functions
Authors: Delaney R. G. , Lahiri S. , Fishman A. P.
Published: April 2021

The present study was undertaken to elicit the temporal sequence of changes in cardiovascular and respiratory function during aestivation. Twelve lungfish (2–6 kg) equipped with ECG electrodes, arterial and buccal cannulae, were studied while aestivating in mud or in artificial cloth-bag nests. The periods of observation ranged from 0·5 to 9·5 months. The mean arterial blood pressure gradually decreased from control values of 20–28 mm Hg to a range of 14–18 mmHg during the first 30 days of aestivation, whereas the heart rate dropped more gradually (22–30 beats/min to 11–16 beats/min in 60 days). Ventilatory frequency increased 2-to 5-fold during the first 30 days of encystment and then returned to the control range (2–10 h) within 45 days. The arterial increased from control values of 25-30 mm Hg to 45-70 mmHg; arterial pH decreased concomitantly from 7·55–7·60 to 7·40–7·26 after the cocoon was formed. The arterial increased from the control range of 25·40 to 50·58 mmHg during the first 10 days and then returned to the control range. Therefore, the sequential cardiopulmonary changes during the onset of aestivation are gradual and do not parallel the decline in oxygen consumption. Aestivating lungfish also respond promptly to sensory disturbances and thus do not appear to be in a deep torpor. Aestivation is pictured as a state of dormancy, gradual in onset, and the consequence of a complicated physiological interplay.
Control of the Pacemaker System of the Nervenet in the Sea Anemone Calliactis Parasitica
Authors: McFarlane I. D.
Published: April 2021

The rhythm of spontaneous nerve-net pulses is reset by intercalated evoked nerve-net pulses. The origin of spontaneous nerve-net pulses can shift during a burst. There seem to be many potential pacemakers, widely distributed throughout the body, but apparently absent from the tentacles. If a spontaneous or evoked pulse in the endodermal slow conduction system (SS 2) occurs during a burst, the nerve-net pulse intervals are increased during a 15–30 sec period following the SS 2 pulse. Additional SS 2 pulses cause a further increase in pulse intervals. Nerve-net bursts are followed by a sequence of muscular contractions. The size of the contraction shown by any muscle group depends on nerve-net pulse number and frequency, the optimum frequency being different for different muscles. It is suggested that the SS 2 pulse action on nerve-net pulse frequency can significantly alter the behavioural output of nerve-net bursts. The SS 2 activity may represent sensory feedback on to the nervous pacemakers.
Vascular Anatomy of the Counter-Current Heat Exchanger of Skipjack Tuna*
Authors: Stevens E. Don , Lam How Man , Kendall J.
Published: April 2021

The anatomy of the counter-current heat exchanger of skipjack tuna is described and the pattern of blood flow is analysed. The pattern of blood flow is from the dorsal aorta, through the exchanger to segmental arteries to the tissues, from the tissues to segmental veins and back through the exchanger to the post-cardinal vein. The vessels in the exchanger are about the same size as systemic arterioles and venules and are about 10 mm long. There are about 125000 of each type in a 2 kg tuna. The velocity of blood flow in the exchanger is about i/8oth of that in the dorsal aorta and post-cardinal vein allowing time for heat transfer. There are many valves in the segmental veins which may be expected because of the resistance offered by the exchanger. The vessels in the tuna heat exchanger are an order of magnitude larger than those in the swim-bladder rete, thus permitting heat transfer but preventing gas transfer.
The Significance of Some Spectral Features in Mating Call Recognition in the Green Treefrog (Hyla Cinerea)
Authors: Gerhardt H. Carl
Published: April 2021

Synthetic calls with a waveform periodicity of 300/sec and a bimodal spectrum attracted female green treefrogs as effectively as natural calls. Effectiveness was markedly reduced if the relative amplitude of the two spectral peaks differed by as little as 10 dB. Optimal frequency bands were 900-1100 Hz in the low range and 2700-3300 Hz in the high. Addition of components at 1800 and 2100 Hz rendered the call less attractive. In the absence of a bimodal stimulus, most females responded to a call containing a single spectral peak in the high or low range. Mating call recognition in the green treefrog is compared with that in the bullfrog.
Aspects of Ionic Transport Mechanisms in Crayfish Astacus Leptodactylus
Authors: Ehrenfeld J.
Published: April 2021

During the uptake of chloride from an external choline chloride solution, electroneutrality appears to be preserved by excretion of base, but base excretion independent of chloride absorption also occurs. Sodium ion uptake from sodium sulphate solutions is compensated by excretion of hydrogen ions, but this has been established only in animals adapted to distilled water. In animals preadapted to running water, the sodium ion influx can be abolished almost totally by amiloride without diminishing ammonium excretion. The net fluxes of sodium and chloride are inhibited by acetazolamide and cyanide. These results are interpreted as indicating that Na+ and Cl− are absorbed chiefly in exchange for H+ and HCO3−, and are discussed in relation to an exchange diffusion mechanism.
Neurophysiological Studies On Echolocation Systems in Awake Bats Producing CF-FM Orientation Sounds
Authors: Suga N. , Simmons J. A. , Shimozawa T.
Published: April 2021

The bats Pteronotus parnelli, P. suapurensis and Noctilio leporinus emit orientation sounds first containing a constant-frequency (CF) and then a frequency-modulated (FM) component. P. parnellii produced a long CF with a second harmonic at 62 kHz to which its auditory system was sharply tuned. In the other two species, the CF was shorter and there was no sharp tuning. Electrical stimulation of the midbrain reticular formation and/or the central grey matter elicited vocalizations which were indistinguishable from those used for echolocation. The electrically-elicited vocalization was enhanced by acoustic stimuli. In P. parnellii, this vocal response was sharply tuned at 62–63 kHz and also to downward sweeping FM sounds. In P. suapurensis and N. leporinus, the vocal responses were prominent only to downward sweeping FM sounds. This indicates that the FM is important to echolocation in all these bats and that the CF component is more essential to echolocation in P. parnellii than to that in P. suapurensis and N. leporinus. The responses of primary auditory neurons to the onset and cessation of pure tone stimuli were due to mechanical events, not due to a rebound from neural inhibition. Masking experiments with P. parnellii indicate that the neural response at the cessation of a CF-FM sound similar to its orientation sound mainly consisted of the response to the FM component and not the off-response to the CF component. During vocalization, self-stimulation was reduced by contraction of middle-ear muscles. This was not due to the acoustic reflex which started to occur with a 6 msec latency.
Calcium-Dependence of Neurosecretion by Exocytosis
Authors: Normann Tom Christian
Published: April 2021

Exocytosis of neurosecretory granules in the corpus cardiacum of the blowfly Calliphora erythrocephala was induced both by electrical stimulation and by depolarization with K+. This secretory activity was quantitatively determined by the frequency of omega figures and vesicle clusters, which are the ultrastructural indications of two distinct phases of the exocytotic process. Experimentally elicited exocytosis was reduced when Ca2+ were omitted from the bathing medium. This result supports the idea that the coupling between excitation (depolarization) and exocytosis involves Ca2+ influx through the axolemma. Barium effectively substitutes for calcium in the secretory process. High levels of magnesium in the bathing medium, however, decreased exocytosis, possibly by interfering with calcium influx.
Experimental Studies on the Circulatory System of the Late Chick Embryo
Authors: White Peter T.
Published: April 2021

A method of preparing the 15/17-day chick embryo for physiological studies is described and the results of an investigation of flow patterns in the circulatory system using oxygen determinations and dye injections is reported. A considerable separation of deoxygenated and oxygenated blood streams occurs in the incompletely divided heart such that a large part of the oxygenated stream flows through the perforated interatrial septum to the left heart for distribution to head, neck, thorax and heart. A mechanism also exists whereby the gut and yolk sac receive blood at an oxygen saturation greater than the remainder of the posterior body. Some quantitative estimates of blood and oxygen flows are made and the circulatory system of the late chick embryo is compared with that of the foetal mammal.
Interneurones in Crab Connectives (Carcinus Maenas (L.)): Directional Statocyst Fibres
Authors: Fraser Peter J.
Published: April 2021

Five interneurones in each connective respond directionally to rotation of a crab. Each seems to be activated by one direction of fluid flow in one statocyst canal. The anatomy of two is known and correlates well with a direct input from the receptors of one statocyst. Three of the fibres have input from leg joint proprioceptors.

The swimming reflex and a complicated turning reflex are evoked on rotation of a minimally restrained crab. It is likely that the statocyst interneurones are involved in these and other behaviour patterns, including the rearing reflex and sideways walking.
Interactions Between Neurones Mediating Tuft Withdrawal in Tritonia Hombergi
Authors: Dorsett D. A. , Willows A. O. D.
Published: April 2021

The seven neurones that command the three stages of branchial tuft withdrawal interact by electrotonic and chemically mediated polysynaptic pathways.

The pleural tuft retractors, L and R Pl 6, make electrotonic synapses with the ipsilateral neurones Pd 2, which cause retraction of the tips of the tufts.

The chemically transmitting pathways, between these and other retractor neurones, are mostly reciprocal and can be classified as weak or strong. The former are small in amplitude, with long latencies (1–3 sec) and are labile to repeated activation; the latter are of large amplitude and shorter latency (0·5–0·8 sec), but may still show decrement with repeated use. Frequently the p.s.p. shows indications of 1:1 correlation with the spike pattern in the driven neurone, but the long latencies require the presence of at least one interneurone in the pathway.

The progressive spread of the behavioural response (withdrawal of the tips, complete unilateral withdrawal, complete bilateral withdrawal of all tufts), which occurs with increasing stimulus intensity, is not dependent on a central hierarchy in the activation of the tuft retractor neurones. Reciprocal feedback leads to a general increase in central excitability, the threshold for more extensive responses being probably determined largely by the sensory input to individual neurones.

The unique pleural cell R Pl 5 is exceptional, both in the variety of motor activity it commands and in the absence of reciprocal connexions from other retractor neurones.