bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical potentials from the eye and optic nerve of Strombus: effects of electrical stimulation of the optic nerve
Authors: Gillary Howard L.
Published: April 2021

Photic stimulation of the mature eye of Strombus can evoke in the optic nerve ‘on’ activity in numerous small afferent fibres and repetitive ‘off’ bursts of afferent impulses in a smaller number of larger fibres. Synchronous invasion of the eye by electrically evoked impulses in small optic nerve fibres (apparently the ‘on’ afferents, antidromically activated) can evoke a burst of impulses in the larger ‘off’ fibres which propagate away from the eye. Invasion of the eye via one branch of optic nerve can evoke an answering burst in another branch. Such electrically evoked bursts are similar to light-evoked ‘off’ bursts with respect to their impulse composition, their ability to be inhibited by illumination of the eye, and their susceptibility to MgCl2 anaesthesia. Invasion of the eye by a train of repetitive electrically evoked impulses in the absence of photic stimulation can give rise to repetitive ‘off’ bursts as well as concomitant oscillatory potentials in the eye which are similar to those normally evoked by the cessation of a photic stimulus. The electrically evoked ‘off’ bursts appear to be caused by an excitatory rebound following the cessation of inhibitory synaptic input from photoreceptors which can be antidromically activated by electrical stimulation of the optic nerve. The experimental results suggest that the rhythmic discharge of the ‘off’ fibres evoked by the cessation of a photic stimulus is mediated by the abrupt decrease of inhibitory synaptic input from the receptors.
Egg Diapause in Ephippiger Cruciger (Orthoptera: Tettigoniidae): II. The Intensity and Elimination of the Final Egg Diapause
Authors: Dean R. L. , Hartley J. C.
Published: April 2021

Unlike the initial diapause in Ephippiger cruciger, the late embryonic diapause occurs in every egg in natural environmental conditions. It is eliminated by one relatively prolonged period of cooling and the proportion of eggs completing diapause development increases with increased cooling time. Diapause is most effectively eliminated through the range of 4–12 °C over a period of 3–4 months. The optimal hatching temperature is lower than the optimal pre-diapause developmental temperature. There is evidence to show that although diapause development and post-diapause development can both proceed at some temperatures, a period of more intense cooling accelerates the processes. The intensity of diapause is not affected by the duration of exposure to high temperature prior to cooling. A comparison between the initial diapause and the second diapause is presented which suggests that the two types of diapause are alternative solutions to the same environmental problem.
Egg Diapause in Ephippiger Cruciger (Orthoptera: Tettigoniidae): III. Abnormal Development Through the Final Egg Diapause
Authors: Dean R. L. , Hartley J. C.
Published: April 2021

Normally the egg of Ephippiger cruciger is subject to diapause when the embryo is almost fully developed. Most eggs die or develop erratically and slowly when chilled for some time at earlier non-diapausing stages. However, after 2 or 3 months’ cooling at a stage just before catatrepsis a few eggs developed more rapidly than usual and hatched without intervention of a diapause, at a temperature that is normally too high to allow diapause development to proceed. A possible mechanism, involving the neurosecretory system, for this diapause pattern is suggested.
A circadian rhythm in the locomotor behaviour of the giant garden slug Limax maximus
Authors: Sokolove P. G. , Beiswanger C. M. , Prior D. J. , Gelperin A.
Published: April 2021

The locomotor activity of the garden slug Limax maximus was examined for components of circadian rhythmicity. Behavioural (running wheel) studies clearly demonstrated that the activity satisfies the principal criteria of circadian rhythmicity. In constant darkness at a constant temperature, the locomotor activity freeran with a period of about 24 h (range 23·6–24·6 h). The rhythm was also expressed in constant light with a period for individual slugs that tended to be shorter in LL than in DD. The period of the rhythm was temperature compensated (11·5–21·5 °C) with a Q10 approximately equal to 1·00. The locomotor rhythm could be entrained to 24 h LD cycles such that the circadian activity peak occurred during the dark. The phase angle between the onset of activity and lights-off was not fixed, but was a function of the photoperiod of the entraining light cycle.
The Uptake of Cadmium Into the Haemolymph of the Shore Crab Carcinus Maenas: The Relationship With Copper and Other Divalent Cations
Authors: Wright D. A.
Published: April 2021

When Carcinus was exposed to 20 μ-mol 1-1 cadmium, the haemolymph cadmium level was initially dependent upon the salinity of the external medium. After 14 days the mean haemolymph cadmium level in 50% s.w. animals was nearly twice that of 100% s.w. animals. This trend was not sustained, however, and the situation was complicated by occasional inconsistent values.

In both in vivo and in vitro conditions nearly all the haemolymph cadmium becomes bound to haemolymph protein within a few days. The relationship between haemolymph cadmium, copper and protein concentration has been investigated. Although the latter are highly correlated with each other, cadmium formed a significant positive relationship with haemolymph copper (r = 0·523) and protein (r = 0·533) only after 3−4 weeks uptaike. Exposure to 20 μ-mol 1-1 cadmium has no obvious effects on haemolymph protein and copper concentrations, which are clearly dependent on feeding status. Mortalities among experimental animals were often preceded by a rise in haemolymph cadmium concentration. This is usually seen before there are any obvious signs of tissue breakdown.

Urine cadmium loss is probably unimportant as a pathway for the elimination of this metal. Urine cadmium concentrations often exceeded serum cadmium levels indicating that cadmium may sometimes be eliminated in bound form.
Body Weight and the Haematology of the American Plaice Hippoglossoides Platessoides
Authors: Smith John Clegg
Published: April 2021

The relationship between haematological variables and body weight (W) is studied in the American plaice. Haematocrit, haemoglobin concentration, and cell volume and numbers are directly correlated with W, indicating that small fish have low blood oxygen solubility in spite of a high weight specific oxygen consumption . Examination of analytical models of the branchial apparatus suggests that, in small fish, is lowered to minimize blood viscosity and that a high is maintained by increasing the arteriovenous oxygen partial pressure difference. Mean cell haemoglobin content is positively correlated while mean cell surface area per unit haemoglobin tends to be negatively correlated with W. Mean erythrocyte residence time in the secondary lamellae is shown analytically to increase with W, possibly accounting for these relationships.
The Locust Jump
Authors: Heitler W. J.
Published: April 2021

The flexor and extensor tibiae muscles of the mesothoracic leg have a constant lever ratio of about 2:1 throughout joint rotation. The mesothoracic tibiae can only flex to 25° about the femora, while the metathoracic tibiae, because of their specialized geometry, can flex almost parallel to the femora. Full metatibial flexion increases the mechanical advantage of the flexor muscle relative to the extensor at full flexion, and increases the vertical component of the thrust produced by tibial extension in a jump. A region in the dorsal proximal cuticle of the metatibia is stiff when stretched but buckles when compressed. The tibia is thus rigid under extensor stress, but bends under flexor stress. Metatibial bending can enable the proximal region of the tibia to become fully flexed even if the distal region is prevented from flexing fully, and may reduce the inertial shock to the femur when the tibia reaches full extension in a kick.
Acoustic Orientation in the Cricket Teleogryllus Oceanicus (Le Guillou)
Authors: Bailey Winston J. , Thomson Peter
Published: April 2021

New information is presented on acoustic orientation in crickets following a comparison between a species with a discontinuous song pattern, Scap-sepidus maginatus (Murphey & Zaretsky, 1972) and one with a continuous song pattern, Teleogryllus oceanicus. The females acuity for side discrimination is ±10° from the body axis whereas the total phonokinetic response shows a greater degree of error. Females can scan their turn angle to target angles beneath 6o°. Error is expressed in terms of information loss through the total behavioural sequence. The cricket does not orient while moving, requires no fixed leg position during the stop for effective orientation and can establish source direction on the basis of at least two syllables. Evidence of differential anterior and posterior tympanic membrane function is suggested.
Mechanisms for Directional Hearing in the Sea Catfish (Arius Felis)
Authors: Tavolga William N.
Published: April 2021

The marine catfish (Arius felis) uses directional hearing for the acoustical detection of obstacles, and is primarily dependent on the vector components of near-field acoustics. Directional sound, detected as lateral line action potentials, produces the strongest response on the side toward the stimulus. Responses are maximal in the 50–150 Hz range. The swim bladder is asymmetrical as a sound generator (7 dB front-to-back ratio). As a sound receiver, the swim bladder is even more directional (24 dB front-to-back ratio at 100 Hz). It is concluded that directional response to sound in fishes can involve the interaction of at least two mechanisms, in this case the lateral line and the swim bladder.
Miniature Potentials, Light Adaptation and Afterpotentials in Locust Retinula Cells
Authors: Tsukahara Y. , Horridge G. A.
Published: April 2021

In dark-adapted retinula cells of the locust, the miniature potentials or bumps have amplitudes of 3–7 mV when recorded in the dark-adapted state with bevelled electrodes at very low light levels. For a sample of N × 378 they had a mean amplitude of 4·55 mV and s.d. 1·59 mV. These are called dark-adapted bumps, and their distribution of amplitudes is presumably a component of the noise of the visual signal in addition to the irregularity of occurrence of bumps.

The afterpotential which follows an intense flash is caused by the summation of bumps which become individually visible as they decline in frequency over a period of many minutes after the stimulus. When recorded over a period from 17 to 23 min after the stimulus, the amplitude of these light-induced dark bumps in a sample of N = 231 had a mean of 2·89 mV and s.d. of 0·92 mV. They also have a shorter duration than dark-adapted bumps.

Light-adapted bumps, which are defined as bumps which arise when light of low intensity falls on light-adapted cells, are statistically indistinguishable in amplitude or duration from light-induced dark bumps. The reduction in size, as compared to dark-adapted bumps, cannot be attributed to a change in membrane potential or to an increase in membrane conductance, which actually decreases during the period of decline of the after-depolarization. Therefore in the light-adapted state, each bump is caused by the opening of fewer sodium channels, or of less effective sodium channels than in the dark-adapted state.
A Respiratory Rhythm in Sea Anemones
Authors: Jones W. C. , Pickthall Veronica J. , Nesbitt S. P.
Published: April 2021

Continuous recording of the O2 content of sea water containing an Actinia equina or a Metridium senile has revealed the occurrence of periodic deflexions on most of the records obtained. The deflexions are probably caused by the release of coelenteric fluid via the mouth. The average period of the rhythm varied from 24 to 43 min (14−15 °C). The period increased in darkness, but was unaffected by feeding, brief mechanical or electrical stimulation, longitudinal bisection of the column and excess KCl or MgCl2; 1·6 mm-KCN abolished the rhythm. The O2 depletion rate did not increase when the anemone contracted in response to stimulation, but it did after feeding, exposure to darkness, or the application of MgCl2. It decreased in the presence of excess KCl. These changes may result from alterations in shape of the anemone. The mechanism for the release of coelenteric fluid has yet to be elucidated. Calculations indicate that from to of the total O2 requirement may enter the tissues from the coelenteron, the remainder being taken up via the ectoderm.
The Effect of Progressive Hypoxia on Respiration in the Toad Bufo Marinus
Authors: Boutilier Robert G. , Toews Daniel P.
Published: April 2021

As Bufo marinus became progressively hypoxic over a period of 90 min, there was a rise in arterial pH, presumably brought about by hyperventilation. The alkalosis gradually disappeared when oxygen levels became very low. It is suggested that this is the result of a respiratory or a metabolic pH adjustment, or both. Hypoxic animals developed a characteristic breathing pattern in which discrete periods of lung ventilations alternated with buccal oscillations or respiratory pauses. A pronounced bradycardia was associated with the concomitant decline of inspired and arterial . Although respiratory rates were greater than normal resting values in the initial stages of post-hypoxia, the pre-exposure breathing pattern was quickly restored. Following recovery from bradycardia (60 min), the breathing rates, arterial blood gases and pHa returned to normal within 30 min.
AN ANALYSIS OF CHANGES IN BLOOD pH FOLLOWING EXHAUSTING ACTIVITY IN THE STARRY FLOUNDER, PLATICHTHYS STELLATUS
Authors: Wood Chris M. , Mcmahon B. R. , Mcdonald D. G.
Published: April 2021

Exhausting activity results in a marked and immediate drop in blood pH which gradually returns to normal over the following 6 h. The acidosis is caused largely by elevated levels, which vary inversely with pH. Blood lactate concentration increases slowly, reaching a maximum at 2−4 h post-exercise, and contributes significantly to the acidosis only late in the recovery period. The slow time course of lactic acid release into the blood permits temporal separation of the peak metabolic acidosis from the peak respiratory acidosis. Evidence is presented that a metabolic acid other than lactic also makes a modest contribution to the pH depression during the recovery period.
Further Studies On the Peripheral Auditory System of ‘CF-FM’ Bats Specialized for Fine Frequency Analysis of Doppler-Shifted Echoes
Authors: Suga Nobuo , Jen Philip H.-S.
Published: April 2021

In the mustache bat (Pteronotus parnellii rubiginosus), the cochlear microphonie (CM) recorded from the round window is sharply tuned at 61 kHz and shows a prominent transient response to a tone burst at about 61 kHz (i.e. its amplitude increases exponentially at the onset of the stimulus and decreases at its cessation). In terms of the time constant (1·1± 0·3 ms) and the resonance frequency (61·1±0·43 kHz) of this transient response, the Q of this system, assumed to correspond to a second-order filter, is 204 + 57. Peripheral neurones sensitive to 61 kHz have a very sharp excitatory area (or tuning curve). The Q of a tuning curve markedly increases with the rise in best frequency up to 61 kHz and decreases beyond 61 kHz. The Q value of a single neurone with best frequencies between 60·76 and 61·75 kHz is 210±189. If the assumption that the CM is directly related to the mechanical motion of the basilar membrane is correct, the very sharp tuning curves of single neurones at about 61 kHz could be simply due to the mechanical timing of the basilar membrane. Since this animal predominantly uses a 61 kHz sound for echolocation and peripheral auditory neurones show a low threshold and extremely sharp tuning at about 61 kHz, its peripheral auditory system is specialized for the reception and fine-frequency analysis of the principle component of orientation sounds and echoes. Sharply tuned neurones can code a frequency modulation as small as 0·01%, so that the wing beat of an insect would be easily coded by them. Unlike the CM, N1 is tuned at 64 kHz. This difference in best frequency is simply due to the properties of a sharply tuned resonator and N1, and not due to a mechanism comparable to lateral inhibition.
The Effect of Sectioning Cranial Nerves V, VII, IX and X On the Cardiac Response of the Dogfish Scyliorhinus Canicula to Environmental Hypoxia
Authors: Butler P. J. , Taylor E. W. , Short S.
Published: April 2021

Exposure of the dogfish to rapidly induced hypoxia caused an initial, large reduction in heart rate to 32 % of its initial normoxic value. When of inspired water reached its lowest level, heart rate increased to 65 % of its normoxic value and this rate was maintained until was returned to normal. Bilateral section of the branchial and pharyngeal branches of either cranial nerve IX or cranial nerve X had no significant effect on the cardiac response to rapidly induced hypoxia. Bilateral section of the pharyngeal and branchial branches of both of these cranial nerves abolished the initial large reduction in heart rate in response to rapidly induced hypoxia; heart rate fell steadily to 40 % of its initial normoxic value after 3 min. Bilateral section of cranial nerves V and VII had a similar effect, with heart rate reaching 62 % of its normoxic value, 3 min after exposure to rapidly induced hypoxia. When the four cranial nerves were bilaterally sectioned together, there was no significant change in heart rate after 3 min exposure to rapidly induced hypoxia. It is concluded that the oxygen receptors responsible for the brady-cardia elicited in dogfish by environmental hypoxia are innervated by cranial nerves, V, VII, IX and X and that if receptors in the C.N.s. are involved in the response, their role is minimal.
A Note on the Effects of Different Doses of Thyroid on The Fowl
Authors: Hutt F. B.
Published: April 2021

Reports of the effects of thyroid feeding on fowls published to date by various investigators show some lack of uniformity. Giacomini (1924) and B. Zavadovsky (1925) have noted depigmentation of plumage when fresh thyroid gland was given orally in doses which, though not stated exactly, were relatively large. The latter writer also obtained the same result with dried preparations.
The Rate of Eye-Growth and its Variation In Gammarus Chevreuxi
Authors: Bělehrádek J. , Huxley J. S.
Published: April 2021

The eye of Gammarus chevreuxi has served several times as an object for genetical observations. We have accordingly thought it useful to undertake a more detailed study of certain quantitative features of its development.
Nitrogen-Excretion in Selachian Ontogeny
Authors: Needham Joseph , Needham Dorothy Moyle
Published: April 2021

The investigations to be described in this paper were originally undertaken in order to throw light on the utilisation of protein as a source of energy by the developing selachian embryo. It has been shown that in the case of the chick (Needham (24), Fiske and Boyden (14)) and of the frog (Bialascewicz and Mincovna (4)) there exists a peak in the intensity of protein breakdown during embryonic life, on each side of which the catabolism of these substances is much diminished. In the case of the mammal (cow and sheep, Lindsay (23) and others) the descending limb of the curve has alone been observed. Our intention was to extend these investigations to a selachian egg, and we obtained several interesting results, although special difficulties were encountered, e.g. (a) the lack of any good series of weighings of selachian embryos, and (b) the remarkably high concentration of urea in elasmobranch tissues, which makes it difficult to regard it wholly as a waste-product.
Temperature and Heart Rate in Chick Embryos
Authors: Parpart E. R. , Glaser Otto
Published: April 2021

In accordance with expectation, the embryonic chick heart exposes recurrently temperature characteristics of the orders 8,200, 14,200, 16,400, 18,300, 20,500 and 25,200. These are found in both myogenic and neurogenic hearts but not with the same frequencies. These two periods of development also differ in the localisation of critical points. So far μ. = 8,200, 14,200 and 18,300 have been exposed in embryos only by Fundulus’, the remaining three orders however are recurrent also in the embryogeny of Limulus. Two orders not included in this list (5000 and 11,000) are rare, yet, even so, not restricted to any one of the three forms. These facts, together with their implications, suggest for heart rhythm in Limulus, Fundulus and the Chick, an underlying physical-chemical mechanism in structure identical for all three types of heart at all stages of development, and differing in neurogenic stages only by a revision of the myogenic time relations.
On Genital Maturity in an Immature Soma
Authors: Mirskaya L. , Crew F. A. E.
Published: April 2021

In the urine from a pregnant woman there are to be found certain physiologically active factors, regarded by Zondek and Aschheim as an elaborated product of the anterior lobe of the pituitary, profoundly influencing the activity of the ovary of rat and mouse, and thus indirectly invoking oestrus. The effect of the injection of urine from a pregnant woman upon the immature female mouse is a maturation of the genital system.
On Phosphorus Metabolism in Embryonic Life
Authors: Needham Joseph , Needham Dorothy Moyle
Published: April 2021

An investigation was made of the phosphorus metabolism of several marine invertebrate eggs (two echinoderms, one gephyrean annelid, and two Crustacea). The distribution of phosphorus-containing compounds was measured before and after development had taken, place. Data are given for the total and lipoid phosphorus, the total water-soluble and stable organic water-soluble phosphorus, the inorganic ortho-and pyro-phosphate, the phosphoprotein and the nucleoprotein. During the development of the sand-crab (Emerita analoga) water is absorbed from the environment, as in the well-known cases of the frog, the trout, and various cladocerans. The egg shell of the brine-shrimp (Artemia salina) contain both calcium and haematin, offering thus a parallel with the shell of avian eggs. During the development of the sanddollar egg (Dendraster excentricus) there is an increase in total phosphorus per unit weight of dry solid. It is pointed out that this absorption of an element from the sea water by the embryo must be taken into account in considering the penetration of marine organisms into fresh water, if, as seems probable, the phosphorus concentration in an aqueous environment may act as a limiting factor. The spicules of the sanddollar pluteus probably contain inorganic phosphate, in quantity roughly corresponding to the amount taken in by the developing egg from the sea water. In all cases so far studied the extent to which lipoid phosphorus is transformed into other forms of phosphorus during embryonic life is proportional to the amount of lipoid phosphorus present at the time of fertilisation. Included in the large stores found in certain eggs there is a fundamental quota which no egg can do without, though this may be, reckoned in absolute values, very small. A computation shows that the contribution of one echinoderm spermatozoon to one egg is of the order of a ten-thousandth part of the phosphorus which is there already. The analyses reported in this paper indicate that, in spite of the large increase of visible nuclear matter during echinoderm development, there is no corresponding synthesis of nuclein. The formation of the chromatin of the nuclei must therefore consist in an organisation of preformed nucleic acids into structural arrangement and not in a manufacture of these compounds by chemical means from other raw materials. Nuclein synthesis, however, certainly occurs in some eggs, and study of the relevant investigations of other workers leads to the conclusion that it is associated with uricotelic metabolism, terrestrial development, and the properties of cleidoic embryos. Wherever the purine ring is synthesised by embryonic cells for nitrogen excretion, there a notable synthesis of the purine ring for cell-nuclei is also found : whatever this is not so, there the eggs are provided by the parent organism with sufficient nuclein for the needs of the embryos.
The Effect of Carbon Dioxide On the Occurrence of Non-Disjunction In Drosophila
Authors: Mottram J. C.
Published: April 2021

The fact that X-rays and radium produce permanent changes in the mechanism of heredity (originally observed by Mavor (1) for non-disjunction and by Muller(2) for mutations) has been widely confirmed by many workers(3). Apart from these radiations no other agent has been found to effect heredity similarly, except for the claim made by Harrison and Garrett (4) that feeding the larval of several species of Lepidoptera on metallic salts results in melanotic mutations.
Changes in Calcium Transport Across Calliphora Salivary Glands Induced by 5-Hydroxytryptamine and Cyclic Nucleotides
Authors: Berridge Michael J. , Lipke Herbert
Published: April 2021

The efflux of 45Ca from prelabelled salivary glands was studied under a variety of conditions. 5-Hydroxytryptamine (5-HT) or cyclic AMP caused a large release of label most of which entered the saliva. The ionophore A23187 caused a similar release of calcium but EGTA had no effect.

The presence of an active calcium pump on the lumenal surface was investigated further by studying calcium transport across the gland. This transport of calcium, which provides a measure of calcium entry into the cell, was very sensitive to 5-HT concentration but little affected by cyclic AMP. The small cyclic AMP-dependent transport was depressed by 8-bromo cyclic GMP with a parallel fall in the rate of fluid secretion.

These studies provide more direct evidence that 5-HT acts to stimulate the entry of external calcium in addition to mobilizing internal calcium.
Respiratory Gas Exchange in the Resting Starry Flounder, Platichthys Stellatus: A Comparison With Other Teleosts
Authors: Wood Chris M. , McMahon B. R. , McDonald D. G.
Published: April 2021

A wide range of respiratory, ventilatory, and cardiovascular parameters have been recorded under completely resting conditions in the starry flounder (Platichthys stellatus), a generally inactive benthic teleost. The results differ in a number of important respects from those of a previous study on the same species. The present data have also been compared with those reported for the active pelagic rainbow trout (Salmo gairdneri) and for other teleost species. Of particular note in the flounder, relative to the trout, are low arterial and venous ’s, a low arterial-venous O2 content difference, a low transfer factor and nigh diffusion gradient for O2 across the gills, a high in vivo blood O2 affinity, a high cardiac output and stroke volume accompanied by a low peripheral vascular resistance, a low ventilation volume, a low ventilation-perfusion ratio, and a low capacity-rate ratio for O2 exchange at the gills. Parameters of CO2 transport and acidbase regulation appear conventional, though blood CO2 contents and lactate concentrations are low. The respiratory strategies of inactive versus active, and benthic versus pelagic teleosts are discussed.
The Feeding Response ofRhodnius Prolixusto Blood Fractions, and the Role of Atp
Authors: Smith J. J. B.
Published: April 2021

Second-instar larvae of Rhodnius prolixus will gorge on washed human erythrocytes suspended in Ringer, but not on plasma, either with or without platelets. The ED 50 of erythrocytes is 4·5 vol of packed cells per 1000 vol of Ringer. Erythrocyte ‘ghosts’ are non-stimulatory, whereas the haemolysate induces gorging. Phagostimulation by ‘ghosts’ is restored by resealing them in 1 mm adenosine triphosphate. Evidence is presented that Rhodnius responds to blood via a release of ATP from a few erythrocytes close to the epipharyngeal sense organs.
Electrogenic Na+ Transport in A Crustacean Coxal Receptor
Authors: Mirolli Maurizio
Published: April 2021

The response of the coxal receptors of the crab Scylla serrata to step stretches consisted of a partial action potential, Va, followed by a steady-state depolarization, Vs. The input resistance of the fibre was reduced during Vs. In the absence of stimulation, the dendrites of the receptors depolarized when external Na+ was substituted with choline or Li+, and when the external K+ concentration was increased or decreased. The dendrites also depolarized when ouabain was added to the saline. The amplitude of both Va and Vs was dependent on external Na+. In cells which were depolarized by ouabain, the amplitude of Vs increased when the K+ concentration of the saline was reduced. V s , was followed by a small, but long-lasting, after-potential which was depolarizing when the membrane potential was between −70 and −60 mV. In cells depolarized by ouabain or by low K+ saline, the after-potential became hyperpolarizing. When trains of brief stretches (each 5 ms in duration) were used as stimuli, the cells responded with trains of Va responses. During this tetanic stimulation the cells hyperpolarized; cessation of the stimulus train was followed by a long-lasting hyperpolarization (PTH). PTH was abolished in Li+ saline, in low K+ saline, and in the presence of ouabain. In control or in low K+ saline, PTH was not accompanied by a decrease in the input resistance of the fibres. It is concluded that an electrogenic Na+ pump (or equivalent process) contributes a substantial fraction of the membrane potential of the unstimulated coxal receptors. Pump activity could be increased by Na+-loading the distal part of the cells with trains of Va responses. By contrast, during the steady-state response to stretch, the pump was not activated.
Neurobiology of the Gorgonian Coelenterates, Muricea Californica and Lophogorgia Chilensis
Authors: Satterlie Richard A. , Case James F.
Published: April 2021

Electrical or mechanical stimulation of Muricea californica or Lopho- gorgia chilensis colonies resulted in withdrawal of polyps in the immediate vicinity of the stimulation point. Additional stimulation did not result in further spread of polyp retraction. Electrical activity was recorded from a colonial conduction system not restricted to the area of polyp withdrawal. Conduction velocity in this conduction system decreased with increasing stimulus number and distance from the stimulation point. Polyp withdrawal in Muricea occurred concomitantly with a burst of facilitating electrical impulses. The withdrawal burst was always preceded by impulses of the colonial conduction system. The pattern of colonial behaviour in gorgonians depends upon the conduction properties of the colonial conduction system, the conduction system(s) of each individual polyp, and the pathways connecting the two. Polyp tentacles bend to the oral disk when presented with liver extract. A burst of electrical impulses was recorded from Muricea polyps during chemical stimulation. These bursts exhibited apparent adaptation and presumably represent muscle potentials resulting from chemoreceptor activation.
The control of walking in orthoptera
Authors: Burns M. D. , Usherwood P. N. R.
Published: April 2021

A brief description is given of the anatomy, innervation and mechanical properties of the extensor tibiae muscles of the locust. Each is innervated by a ‘fast’ (FETi) and ‘slow’ (SETi) excitatory axon, one branch of a common inhibitor (Cl) and a fourth small axon (DUMETi). The prothoracic and mesothoracic extensors contract more rapidly than the metathoracic muscle but exhibit a stronger ‘catch’, which can be relaxed by Cl or FETi activity.

Records were made of electrical activity in the extensor motor nerves in all the legs of locusts and lubber grasshoppers. During standing only the SETi axons were active. During straight line walking in the locust all three motor axons were active, except in the metathoracic leg. A detailed descrip­tion of the activity pattern of each axon is given. The activity in the grass­hopper was similar, but rather more variable. Measurements were made of the mechanical responses of the extensor muscles to these patterns of activity. As walking speeds increased the response to SETi activity approached a constant tension or muscle length which could be strongly modulated by the phasic contractions due to FETi activity. It is suggested that the timing of SETi activity is only important at low walking speeds, and that at high speeds it simply provides a return force for the flexor muscle. The Cl produces a slow effect and fires at the wrong time in the step to phasically relax the prothoracic or mesothoracic extensors, so it is suggested that its main role is in the relaxation of coxal muscles. The sources of motor neurone activity are discussed.
Studies on the Nutrition of Blow-Fly Larvae
Authors: Hobson R. P.
Published: April 2021

The mid-gut in Lucilia larvae can be divided into three distinct regions (termed anterior, middle and posterior segments). Histologically the anterior and posterior segments are similar. In a feeding larva the cells are highly vacuolated and contain fat ; in a starved larva the cells are deeply staining and non-vacuolated. In the middle segment the cells are always deeply staining and free from vacuoles and fat, whatever the state of nutrition. The hydrogen-ion concentration varies along the gut and with the nature of the food. With liquefied meat as food, the pH is 7·5−8·0 in the crop, 7·5 in the anterior segment, 3·0−3·5 in the middle segment, 7·5−8·3 in the posterior segment, and 8·0−8·5 in the hind-gut. With fresh gelatine (pH 7·0) as food, the values are the same except in the crop and anterior segment, for which the figures are respectively pH 7·0 and 6·5. It has been suggested that the acidity in the middle segment may be due to an acid secretion, the most likely component being phosphoric acid. The alkaline reaction in other parts of the gut is probably caused by ammonia, which is present in the gut-contents and excreta. Tryptase, peptidase and lipase are present in the mid-gut, the enzymes being concentrated in the anterior and posterior segments. The proteolytic enzymes persist in the excreta and some extra-intestinal digestion, therefore, can occur without the aid of micro-organisms. Carbohydrate-splitting enzymes are absent except for a feeble secretion of amylase in the salivary gland. By combining the evidence from various sources, I have attempted to obtain a complete picture of the process of digestion, which I suggest is as follows:

The food is stored unchanged in the crop and, passing into the mid-gut, is rapidly forced into the middle segment. Some absorption of water and simple products of bacterial action occurs along the anterior segment, the concentration of the food being completed in the middle segment where the acidity prevents digestion. The food, by now of a pasty constituency, passes into the posterior segment, dissolves in the alkaline fluid and is digested and absorbed. The digestive enzymes are secreted in the anterior and posterior segments, but digestion does not progress far in the anterior segment owing to the rapid passage of the food.
Potential Differences Across Natural Membranes Separating Unlike Salt Solutions
Authors: Brooks S. C. , Giese A. C. , Giese R. I.
Published: April 2021

Loeb and Beutner (1911) showed that when the cutinised epidermis of the apple separates two unlike solutions of electrolytes, a potential difference develops, which they interpret as being due to exchange of ions, mainly cations, across the epidermis. They suppose that the faster-moving ions tend to penetrate more rapidly through the epidermis, and hence build up a potential difference.

Michaelis (1925) gives a mathematical development of essentially this theory to explain his own experiments with “dried” celloidin membranes which are permeable to cations but not to anions, and which, like the apple epidermis, develop a potential difference which is constant for a considerable period of time.

Recently, Mond and Hoffmann (1928) described a membrane made of celloidin and Rhodamin B, which is selectively anion permeable. This was followed by Höber and Hoffmann’s (1928) study of a mosaic membrane made up of alternating areas of cation permeable celloidin and anion permeable celloidin-Rhodamin B. In this case the potential difference obtained was considerably lower than that for either the celloidin or celloidin-Rhodamin B membranes separately, the potential differences of the two areas being in opposite directions and tending to annul one another.

The cutinised epidermis from the inner surface of bulb scales of the onion resembles these membranes in that there is no diffusion of ions through the epidermis from solutions of electrolytes into distilled water (Brooks, 1917).

It, therefore, seemed desirable to study the nature of the potential differences developed by the onion epidermis when it separates two solutions containing ions, with a view to further analysis of the electromotive mechanisms at work.
Studies in the Localisation of Respiratory Exchange in Invertebrates
Authors: Zoond Alexander , Charles Enid
Published: April 2021

The respiratory exchange of the fresh-water crab Potamonautes is almost entirely localised in the gills. This crab can respire and survive in water and in air. In water the ventilation of the gills by the activity of the scaphognathite is indispensable to the maintenance of respiratory exchange. In air the scaphognathite is unimportant; simple diffusion suffices to renew the supply of oxygen at the gills.
The Effect of Increased Metabolic Rate On Renal Function in the Rainbow Trout, Salmo Gairdneri
Authors: Hofmann E. L. , Butler D. G.
Published: April 2021

A highly significant linear correlation was found between glomerular filtration rate and urine flow rate in both freshwater and seawater trout. The percentage tubular reabsorption of water was approximately 33% greater in seawater trout than in freshwater trout. As oxygen consumption increased, the urine flow rate increased in freshwater and seawater rainbow trout. The proportional increase in urine flow with incremental changes in oxygen consumption was approximately the same in fresh water and sea water. A significant positive linear relationship between oxygen consumption and glomerular filtration rate was found in both salinities. The proportional increase in GFR with incremental changes in the oxygen consumption rate was higher in the seawater trout than in the freshwater trout. As oxygen consumption increased, the percentage tubular reabsorption of water decreased in the freshwater trout. No significant relationship between these two factors was found in the seawater trout.
Aerial CO2 Excretion in the Obligate Air Breathing Fish Trichogaster Trichopterus: A Role For Carbonic Anhydrase
Authors: Burggren Warren , Haswell Steve
Published: April 2021

Total oxygen uptake and carbon dioxide excretion and their partitioning between gills and aerial exchange organs have been measured in an obligate air breathing fish, the blue gourami (Trichogaster trichopterus). Measurements were made during normal bimodal breathing and in air-exposed fish. increased during air exposure, but the aerial exchange organs or ‘laby-rinth’ of Trichogaster could assume a highly effective CO2 excretion in the absence of branchial gas exchange. Hence, aerial was greatly increased during air exposure, and the labyrinth gas exchange ratio increased to 0·8 from the value of 0·1 evident during bimodal gas exchange.

The large aerial CO2 excretion in Trichogaster, unobtainable in many air breathing fish, was unaffected by the injection of carbonic anhydrase, but was seriously disrupted in the presence of this enzyme’s potent inhibitor, acetazolamide. In vitro assay for carbonic anhydrase demonstrated the labyrinth epithelium of the gourami to be rich in this enzyme. It is concluded that highly effective CO2 excretion from the labyrinth organs during air exposure in Trichogaster results from dehydration of plasma bicarbonate to molecular CO2 at the catalysed rate; carbonic anhydrase for this purpose being present in the labyrinth epithelium. The distribution of carbonic anyhdrase in the tissues of other air breathing fishes is determined, and its implications to aerial CO2 excretion discussed.
The Mechanics of Labriform Locomotion
Authors: Blake R. W.
Published: April 2021

A blade-element approach is used to analyse the mechanics of the dragbased pectoral fin power stroke in an Angelfish in steady forward, rectilinear progression. Flow reversal occurs at the base of the fin at the beginning and at the end of the power stroke. Values for the rate of increase and decrease in the relative velocity of the blade-elements increase distally, as do such values for hydrodynamical angle of attack. At the beginning and end of the power stroke, negative angles occur at the base of the fin. The outermost 40% of the fin produces over 80% of the total thrust produced during the power stroke, and does over 80 % of the total work. Small amounts of reversed thrust are produced at the base of the fin during the early and late parts of the stroke. The total amount of energy required during a cycle to drag the body and inactive fins through the water is calculated to be approximately 2·8 ×10−6 J and the total energy produced by the fins over the cycle (ignoring the recovery stroke) which is associated with producing the hydrodynamic thrust force, is about 1·0×10−5 J ; which gives a propulsive efficiency of about 0·26. The energy required to move the mass of a pectoral fin during the power stroke is calculated to be approximately 2·6 ×10−7 J. Taking this into account reduces the value of the propulsive efficiency by about 4% to about 0·25. The total energy needed to accelerate and decelerate the added mass associated with the fin is calculated and added to the energy required to produce the hydrodynamic thrust force and the energy required to move the mass of the fins; giving a final propulsive efficiency of 0·18.
An Optical Tachometer for Measurement of the Wing-Beat Frequency of Free-Flying Insects
Authors: Unwin D. M. , Ellington C. P.
Published: April 2021

The wing-beat frequency of flying insects has generally been measured by acoustic methods, but even with modern condenser microphones and frequency-selective amplification the signal available from smaller insects may be inadequate. A microphone had to be placed within 1 cm of the midge Smittia aterrima (Mg.) to produce a satisfactory signal and no signals could be obtained from Thrips sp. (Thysanoptera). Acoustic recordings of flying insects in the laboratory may also be degraded by the excited resonant frequencies of the cage material. The optical tachometer uses the minute changes in the intensity of ambient light reflected from an insect’s beating wings to produce an amplified electrical output at the wing-beat frequency, producing an adequate signal from a very much greater range than would be obtained by acoustic methods. With this device Smittia aterrima could be measured at a distance of 1 m, Drosophila melanogaster Mg, at 1·2 m, and larger insects from a much greater range: Calliphora vicina (R-D.) 7 m, and Bombus sp. 10 m. No difficulty is found when making measurements through the sides of transparent flight cages. The sensitivity of the device seems sufficient for recording Thrips, although this has not yet been tested.
Gas Exchange and Transport During Intermittent Breathing in Chelonian Reptiles
Authors: Burggren Warren W. , Shelton Graham
Published: April 2021

The oxygen and carbon dioxide gas tensions in lung gas and blood from the central and peripheral arteries and veins have been measured in unrestrained, undisturbed turtles (Pseudemys scripta) and tortoises (Testudo graced). Lung and blood gas composition fluctuates widely with intermittent and irregular lung ventilation. The pulmonary gas exchange ratio, which progressively falls during apnoea to as low as 0·2–0·3 in Pseudemys, rises dramatically to over 1·5 during lung ventilation in both species. It is postulated that CO2, which has been passively stored by entering the tissues along gas tension gradients during apnoea, Becomes rapidly eliminated into the lungs during ventilation. In diving Pseudemys the lung has only a limited function as a CO2 sink compared to the tissues, but the lung acts as a large oxygen store, which can be drawn upon during apnoea through periodic increases in lung perfusion. Blood gas tensions in the various systemic arches reflect the proximity of the arch’s origin to the systemic or pulmonary venous blood streams in the ventricle. Thus, the brachiocephalic artery and right aorta have identical blood gas compositions while the composition of the left aorta is intermediate between these and that in the pulmonary. These relationships are unaffected by normal intermittent breathing. However, this does affect both the origin and composition of systemic and pulmonary arterial blood, such that the greatest proportion of oxygenated blood perfuses the systemic vascular bed during lung ventilation, while the greatest proportion of deoxygenated blood perfuses the lungs during apnoea. These data are discussed in the light of the marked cardiovascular adjustments to intermittent breathing, which occur in chelonian reptiles.
Effect of Diet Viscosity on the Operation of the Pharyngeal Pump in the Blood-Feeding Bug Rhodnius Prolixus
Authors: Smith J. J. B.
Published: April 2021

The rate of pumping and total number of pump strokes was recorded whilst Rhodnius prolixus fed on measured amounts of artificial diets. Increasing the viscosity of the diet caused a decline in both the frequency with which the pharyngeal pump operates and the average stroke volume of the pump. In 5th-instar Rhodnius, the stroke volume tends toward a maximum value of about 60 nl at viscosities lower than about 3 cP. Feeding rates (volume per unit time) agree with Poiseuille’s law at high viscosities, but are less than predicted at low viscosities. The maximum power output of the pump occurs at a viscosity between i and 3 cP, which is probably the range of the effective viscosity of blood in tubes with the dimensions of Rhodnius stylets. These results are inconsistent with a hypothesis of a central nervous system ‘oscillator’ controlling the pump muscle, independent of feedback, but are consistent with a model involving peripheral feedback from stretch receptors, with an appropriate delay.
Cinematographic and Electromyographic Analysis of Vertical Standing Jump in the Dog
Authors: Tokuriki Mikihiko
Published: April 2021

The electromyograms of 37 skeletal muscles were obtained using the bipolar wire electrode method in the vertical standing jump of a dog. Their electromyographic patterns were analyzed in conjunction with cinematographic films. Co-contraction of muscles of the extremities was observed during take-off and landing. Electromyograms also revealed that the forelimbs were accelerated against the body just after take-off and that the fore quarters transferred the centre of gravity of the body in a much more complicated movement than the hind quarters. In the floating phase, the muscles of the lower extremities had no activity, apart from some proximal ones. That the muscles of the four extremities exhibited their activity just before landing indicates that the activity may have been controlled by a central programme. In the vertical standing jump, the dog brings the centre of gravity of the body near to the kicking or landing paws by skillful movement of the axial skeleton. Cinematography revealed that, in the leaping gallop gait, the dog makes a similar movement of its axial skeleton.