bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Peristaltic Progression and the Functional Significance of the Dermal Connective Tissues During Burrowing in the Polychaete Polyphysia Crassa (Oersted)
Authors: Elder Hugh Y.
Published: April 2021

Polyphysia excavates its burrow in soft, sublittoral mud by sinusoidal waves of the septate anterior region of the body and the lateral scraping action of the prostomial horns. Associated with discrete, direct peristaltic constrictions, in which the longitudinal muscles shorten to 40%, and the circulars to 80%, of their distended lengths, hydraulic deployment of coelomic fluid converts the periodic advance of the trunk segments into continuous head progression. Direct peristaltic progression advances the body by one-fifth or less of a wavelength per cycle, which is comparable to the figure for earthworm locomotion. A three-dimensional dermal collagen fibre lattice accommodates extensive folding of the cuticle and epidermis while permitting a three-to fourfold increase in the radial dimension of the body wall during peristaltic constriction. Elastic fibre columns oppose the radial distension and control the cuticular folding. These features are seen as adaptations to burrowing in the soft mud habitat. The high degree of body-wall flexibility permits the transition from contracted to distended configuration within the length of one segment. Some three-quarters of the body surface may be in contact with the burrow wall at any one time. Unlike other soft-bodied burrowing animals the force exerted on the burrow wall is unidirectional and the applied pressure is probably small, relatively constant and spread over a wide area.
Nervous Mechanisms Underlying Intersegmental Co-Ordination of Leg Movements During Walking in the Cockroach
Authors: Pearson K. G. , Iles J. F.
Published: April 2021

The activity in identical motoneurones innervating leg muscles of the three thoracic segments of the cockroach has been recorded in (a) normal walking animals, (b) walking animals after lesions to the nervous system and/or amputation of the mesothoracic legs, and (c) restrained de-afferented preparations. The phase of levator motoneurone burst activity of the mesothoracic leg in the metathoracic cycle is almost 0 · 5 for all walking speeds above 2 steps/sec, confirming that a tripod gait is used at all but the slowest speeds. The burst-generating systems in each segment are centrally coupled because in de-afferented preparations there is a tendency for the bursts in the mesothoracic segment to begin near the end of the metathoracic bursts, and vice versa. Sensory input from leg receptors is also important in co-ordinating stepping movements of the different legs since (a) there are some differences in motoneurone activity of de-afferented and walking preparations, and (b) amputation of the mesothoracic legs at the trochanter leads to an immediate change in the co-ordination of the remaining four legs. It is proposed that two mechanisms are important in co-ordinating leg movements in a slow walking cockroach (a) mutual inhibition between levator burst-generating systems in adjacent ipsilateral legs, and (b) an inhibitory reflex pathway from the campaniform sensilla of the trochanter to the burst-generating system of each leg. The second of these two mechanisms may become less important as the walking speed increases.
The Motor Innervation and Musculature of the Antennule of the Hermit Crab, Pagurus Alaskensis (Benedict)
Authors: Snow P. J.
Published: April 2021

The motor innervation and musculature of the medial and distal segments of the hermit-crab antennule have been described anatomically. Intracellular recordings within these muscles and simultaneous monitoring of whole-muscle tension have been used to define the motoneurones and contractile properties of the muscle fibres they innervate. The motor system consists of two fast, two slow and one mixed muscle which are innervated by seven motoneurones. The motor innervation is such that this system may be divided into three components: phasic, phasic-tonic and tonic. The possible involvement of these components in the antennular activities is discussed. The tonic component is adapted to produce fine tonic tension in response to relatively low-frequency (5−10/sec) motoneurone discharge. It is suggested that this may be important for the postural control of appendages which, owing to the density of the environmental medium, are relatively weightless. No evidence of postsynaptic inhibition was found, and this is discussed in relation to the movements of the antennule.
The Mechanism of the Pupal Gin Trap
Authors: Bate C. M.
Published: April 2021

The sensilla inside the gin trap are connected with an intemeurone in the ipsilateral connective above the ganglion in which their axons terminate. This cell is driven by the combined input of many fibres in the afferent bundle; it receives an inhibitory input driven by the contralateral muscle receptor organ and another driven by the contralateral trap sensilla. There is an inhibitory relation between efferent activity on opposite sides of the nervous system. A model is proposed which enhances contrast between the two halves of the nervous system by an inhibitory cross-connexion. The closure mechanism of the gin trap does not fit this model but can be derived from it by a small change in the properties of the ipsilateral junction of triggering sensilla and second-order neurones. A consequence of this theory is that the terminals of the triggering sensilla need not be identified within the central nervous system.
Statocyst-Induced eye Movements in the Crab Scylla Serrata
Authors: Sandeman D. C. , Okajima A.
Published: April 2021

The sensory axons of the thread hair receptors, free hook hair receptors and most receptors of the statolith area of the crab statocyst all project to the same dorsolateral part of the brain. Large sensory receptors which innervate some hairs surrounding the statolith project to a more ventral site, and send some branches across to the contralateral side of the brain. The central projections of oculomotor neurones have a characteristically open branch pattern and their dendritic field corresponds closely with that of the thread hairs. There are no branches extending to the contralateral side of the brain. Intracellular responses from the motor neurones of horizontal eye-movement muscles during nystagmus show that they are probably directly inhibited during a fast-phase movement of the eye opposite to the direction in which they act. During a slow-phase eye movement opposite to their preferred direction the input to the motor neurones is diminished pre-synaptically. Sets of antagonist motor neurones maintain a fairly rigid relationship to one another so that an increase in activity of one set leads to a decrease in the antagonists. Neither this, nor the onset of the fast phase of nystagmus, is governed by proprioceptive input or by the frequency of discharge of the motor neurones themselves.
Isosmotic Regulation in Various Tissues of the Diamondback Terrapin Malaclemys Centrata Centrata (Latreille)*
Authors: Gilles-Baillien M.
Published: April 2021

Osmotic adjustment is achieved by blood and intracellular fluids in the diamond-back terrapin when acclimatized either to fresh water or to sea water. The muscle adjusts its composition to a higher blood osmotic pressure by greater concentrations in ammonia, in taurine and in urea and to a lesser extent in all amino acids (aspartate excepted). The inorganic ion content is not affected. In the bladder mucosa ammonia, taurine and all amino acids are more concentrated in sea-water animals. But essentially urea is responsible for the higher osmotic pressure. Of the inorganic ions only potassium shows a (slight) increase in sea-water animals. In the colon mucosa there is a slight increase in the total amino acid content, in the concentrations of sodium and chloride, and a larger increase in urea. In the jejunum mucosa the concentrations of amino acids, urea and K are much higher in sea-water animals. The results are discussed within the framework of isosmotic regulation of intracellular fluids.
Control of Heart Rate in Cecropia Moths; Response to Thermal Stimulation
Authors: Hanegan James L.
Published: April 2021

The site for regulation of heart rate is the pterothoracic ganglia. Heart rate increases when the animal goes from an inactive to an active state. At low air temperatures the transition is from torpor to warm-up and above 35 °C the transition is from torpor directly to flight. The heart of Cecropia moths isolated from neural connexions to the thoracic ganglia responds directly to temperature changes. In actively flying animals the heart rate increases in response to thoracic heating.
The Circulatory Physiology of Helix Pomatia: I. Observations on the Mechanism by Which Helix Emerges from its Shell and on the Effects of Body Movement on Cardiac Function
Authors: Sommerville Barbara A.
Published: April 2021

1. Helix uses the muscular floor of the mantle cavity to effect several movements. The contraction and relaxation of these muscles is concerned primarily with filling the lung and absorption of oxygen under pressure. The movement is linked with that of the pneumostome, which is open while the floor is depressed and closed when it is raised. An exaggeration of the breathing movements serves to generate the pressure in the cephalopedal haemocoel, which propels the anterior part of the body out of the shell. 2. The rate and regularity of heart-beat vary during the breathing cycle, being slow and irregular when the pneumostome is closed and fast and regular when it is open. 3. Observation of the intact heart of Helix showed changes in the degree of filling indicating an increased blood flow from the haemocoel to the pulmonary veins and heart when the mantle cavity floor was depressed. The total volume of the heart and pericardial cavity was greater at ventricular diastole than at ventricular systole. 4. When the cardiac nerve was severed a significant but inconsistent relationship between the heart activity and the breathing cycle remained. 5. Helix pomatia, H. aspersa, Archachatina, Monodonta and Arion ater all have a semilunar valve on the common aorta directed so as to prevent blood flowing from the aorta into the ventricle. H. pomatia and H. aspersa have a second semilunar valve in the anterior aorta while in Archachatina the anterior aorta passes through a muscular constriction.
The Circulatory Physiology of Helix Pomatia
Authors: Sommerville Barbara A.
Published: April 2021

In isolated heart preparations of Helix pomatia perfused with Hedon Fleig solution, a minimum of 5% Helix blood was necessary for sustained rhythmical beating. In the absence of the first aortic valve the heart was unable to pump fluid against a negative pressure gradient, the frequency of beat was directly proportional and the amplitude of beat inversely proportional to the arterial pressure while the frequency was inversely proportional to the venous pressure. When the first aortic valve was included in the preparation the heart pumped efficiently and the frequency response was reversed in each case.
Studies on the Mechanism Of Chloride Absorption by the Goldfish Gill: Relation With Acid-Base Regulation
Authors: Renzis G. De , Maetz J.
Published: April 2021

Pretreatment of Carassius auratus in artificial media (de-ionized water, sodium sulphate or choline chloride solutions), resulted in simultaneous loss of internal Na and Cl2 variations in the total CO2 and NH3 plasma content; blood pH shifts towards alkalosis in fish treated with sodium sulphate and towards acidosis in fish treated with de-ionized water or choline chloride. Fish kept in de-ionized water and in sodium sulphate solution were compared with control (tap water) fish. Branchial chloride fluxes were studied as a function of external chloride concentration, the accompanying cation being impermeant (choline) or permeant (sodium). For chloride influx saturation kinetics prevails, the maximal rate of uptake being about 3 times faster in sodium sulphate than in fish kept in deionized water, the apparent affinity of the uptake mechanisms (Km) remaining the same. Substitution of choline by sodium increases the maximal rate of influx without changing the Km or efflux in all types of fish. The quantity of base excreted is correlated to the quantity of Cl− absorbed confirming the Cl−/HCO3−exchange process. The degree of linkage between Na and Cl absorption is discussed in relation to the maintenance of acid-base balance by the gill.
Modification of the Motor Reflex Responses Due to Repetition of the Peripheral Stimulus in the Cockroach
Authors: Zilber-Gachelin N. F. , Chartier M. P.
Published: April 2021

In the cockroach Blabera craniifer repeated air puffs to the cerci induce a habituation of the corresponding escape reflex, which we have tried to relate to the transfer properties of the two central relays of the reflex. In this paper transmission through the first relay, the 6th abdominal ganglion (A.G.), was studied both by electrical stimulation of the sensory cereal nerve and by application of natural stimuli (air puffs) on the cerci, while recording simultaneously on the cereal nerve and the abdominal cord, i.e. respectively before and beyond the synaptic relay. The electrical stimulation study shows transmission to be relatively labile. This property is still more apparent if air puffs are delivered. If they are separated by less than about 10 sec the cereal nerve response decreases, which is a sign of a receptor adaptation. For longer intervals, although this adaptation disappears, the response nevertheless decreases on the cord, implicating the ganglionic relay as the centre of a habituation phenomenon. The characteristics of this habituation are the following: with repetition of the stimuli, the response decreases down to a non-zero plateau (decrease of about 50 % if a puff is delivered every 20 sec); it recovers spontaneously if stimulations are suppressed; habituation is potentiated when successive series of habituations followed by spontaneous restorations are accumulated; it is more pronounced as the stimulation frequency is increased; finally, it does not show generalization. These results confirm that the 6th A.G. independently exhibits a real habituation process. The mechanism of this habituation process is discussed. A post-excitatory pre-synaptic depression intrinsic to the reflex’s excitatory synapses themselves is tentatively proposed.
Modification of the Motor Reflex Responses Due to Repetition of the Peripheral Stimulus in the Cockroach
Authors: Zilber-Gachelin N. F. , Chartier M. P.
Published: April 2021

The synaptic transfer properties within the 3rd thoracic ganglion (T.G.) from the abdominal cord axons to the motoneurones has been studied in the cockroach. This ganglion was completely de-afferented except for motor nerve 4, whose links with the muscles of the posterior legs were left intact. The response of one of these nerves to electrical stimulation of the abdominal cord involves activation of 2 types of units : Slow excitatory fibres which have a tonic discharge and respond to each low-threshold abdominal cord stimulation by a transient increase of this firing rate; these units are responsible for muscular tonus and for low amplitude movements (startle reactions). Fast excitatory fibres, which have no tonic discharge and require for their activation higher intensity and frequency of stimulation, i.e. an important temporal and spatial summation. They are responsible for larger and more rapid movements. They fire without any precise chronological relation with the stimuli, often in bursts which continue after the end of the stimulations and cause sudden rhythmic movements. During repetition of the stimuli, the two types of synaptic pathways show both habituation and facilitation through temporal summation and post-tetanic potentiation. These two phenomena persist after the end of the stimulations and have long (minutes) but different time courses. Moreover, habituation always prevails over facilitation if stimulations are continued during a sufficient time. These antagonistic properties existing at the same time might explain the complex way in which the motor responses develop with the application of repetitive trains of stimuli to the cord. The role of these properties in the changes of the reflex motor responses to successive air puffs applied to the cerci has been studied. These properties appear to be responsible for the sensitization of the responses which can be sometimes observed. They lead, in conjunction with the habituation properties of the 6th abdominal ganglion (A.G.), to the disappearance of the escape reflex involving firing of both fast and slow fibres. Finally, they seem to have a minor role in habituation of the startle reactions (involving firing of only the slow fibres) which would be mainly due to the 6th A.G. habituability.
Evidence For an Auditory Function of the Swimbladder in the Cod
Authors: Sand Olav , Enger Per S.
Published: April 2021

Saccular microphonic potentials in cod (Gadus morhua) were recorded by means of implanted electrodes during sound stimulation with different swimbladder volumes. To obtain acceptable acoustic conditions, the experiments were conducted at 6 m depth in the sea. Swimbladder volume had no effect on the microphonic potentials at 100 Hz, whereas its effect was marked at higher frequencies. The sound pressure necessary to evoke microphonic potentials just above the electric background noise was about 20 dB higher for the empty bladder, compared to the full bladder at 300 Hz. The microphonic potentials are ultimately linked to excitation of eighth-nerve fibres, and it is concluded that the existence of gas in the cod swimbladder has a positive effect on hearing sensitivity for all frequencies from a lower transient frequency to the upper frequency limit of hearing. Gas in the swimbladder will furthermore extend the audible frequency range. The upper frequency limit for the saccular microphonic potentials is in good agreement with the upper audible frequency limit determined from behavioural audiograms for cod, thus indicating that this frequency cut-off may be due to inadequacy of the peripheral auditory apparatus.
Directional Sensitivity of Saccular Microphonic Potentials in the Haddock
Authors: Enger P. S. , Hawkins A. D. , Sand O. , Chapman C. J.
Published: April 2021

Microphonic potentials from the sacculus in the haddock have been recorded by implanted electrodes during horizontal vibration of the fish in air. This gives a good simulation of sound stimulation in water. The microphonic potential amplitude was a function of the vibration angle, and from most recording loci maximal amplitudes were obtained for vibration directions parallel to the long axis of the fish. The sensory cells contributing to this response are therefore most sensitive to displacements in the same direction as sound-induced swimbladder pulsations would produce. This result thus supports the theory of an accessory role of the swimbladder in sound reception. Highest sensitivity to vibration directions other than parallel to the long axis of the fish has been obtained from other recording loci. One example of highest sensitivity to a vibration direction at right angle to the long axis of the fish is presented. The findings that different sensory cells appear to have different axes of maximal sensitivity to vibration provides one possible neurological explanation for the ability of fish to detect the direction to a sound source.
The Initiation and Control of Free Amino Acid Regulation of Cell Volume in Salinity-Stressed Marine Bivalves*
Authors: Pierce Sidney K. , Greenberg Michael J.
Published: April 2021

Molluscan cells maintain constant volume in decreasing salinities by releasing intracellular free amino acids as osmotic solute. During a salinity decrease both osmotic pressure and ion concentrations decline simultaneously. Either condition might initiate the amino acid release. Under constant osmotic conditions a decrease in Na+, K+ or Cl− concentration in the medium surrounding the isolated bivalve heart, did not result in an amino acid efflux. On the other hand, removal of Ca2+ and Mg2+ resulted in a vigorous amino acid efflux which continued until the divalent ion concentration was restored. The hypo-osmotically induced amino acid efflux could be partially blocked by raising the external divalent ion concentration. Similarly, lanthanum proved to be an effective blocking agent, both in low osmotic pressures and in Ca2+- and Mg2+-free SW. These results show that salinity-induced free amino acid regulation is initiated by a decrease in external osmotic pressure. The time course of the efflux is dependent on external divalent ion concentration. Finally, the site of divalent ion action is at the external membrane surface. A hypothetical membrane model is proposed.
The Stability of the Free Amino Acid Pool in Isolated Peripheral Nerves of Carcinus Maenas (L.)
Authors: Evans P. D.
Published: April 2021

Isolated peripheral nerves of Carcinus maenas (L.) were capable of maintaining their free amino acid levels steady for the first hour of incubation in saline. The addition of a presumed blood concentration of D-glucose (7 ·2 mg/100 ml) caused a rapid drop in the amino acid levels, whereas incubation in actual fresh samples of blood did not. It is possible therefore that much of the glucose in crab blood might be effectively sequestered into the haemocyte fraction. It is suggested that metabolism might play an important part in the maintenance of the very steep free amino acid concentration gradients across the neuronal membranes of this species. The efflux of amino acids from this tissue is complex. It consists of a slow component T0·5 = 77 ·7 min) and a fast component (T0·5 = 3 ·1 min) which account for about 50% and 40% respectively of the total intracellular radioactivity accumulated after a 20 min incubation. In experiments where the nerves retained connexion with the thoracic ganglion, the levels of amino acids were higher than in controls which were isolated from the ganglion by a ligature. The possible significance of these findings is discussed.
Blood Pressure and Its Hydraulic Functions in Helix Pomatia L.
Authors: Dale B.
Published: April 2021

Blood pressure has been measured in several parts of the haemocoele of a representative terrestrial pulmonate, Helix pomatia. A venous pressure of 8 cm of water is required to overcome the resistance presented by the branchial plexus and to effect the process of ultrafiltration in the renal plexus. Visceral sinus and sub-renal sinus blood is at a pressure barely exceeding this value and need only perform the two named functions before returning to the auricle. Blood in the cephalopedal sinus and general haemocoele of the foot is at a higher pressure, of up to 16 cm, and has obvious hydraulic functions. Partly by review of the literature and partly by direct observation these functions are discussed. The distribution of blood during different states of activity and the importance of the heart in maintaining the high haemocoelic pressure of pulmonates is also briefly discussed.
Central Control of Postural Orientation in Flatfish
Authors: Platt Christopher
Published: April 2021

Visual influences on postural responses mediated by the otolith organs were studied in behavioural and physiological experiments on two species of flatfish, the bothid Citharichthys stigmaeus and the pleuronectid Hypsopsetta guttulata. Ocular compensation to lateral tilt is altered toward a directional light stimulus ; the light effect is independent of the tilt effect, and sums with it. Maximum light effect is roughly one-fourth the magnitude of the maximum tilt response. Single shocks to the optic tectum evoke up to three responses in the cut stump of the ipsilateral vestibular nerve, falling into three latency groups at roughly 5, 10 and 20 msec; all three follow stimulation of the anterior lateral tectum. The two later groups suggest by their delay and extinction at low stimulus rates that their path involves at least one synapse. Some units determined as primary otolith-organ afferents by their response characteristics to lateral tilts show a change in rate following a burst of shocks to the tectum, but no response to single shocks. The usual effect is excitatory, with a latency of 50 –100 msec, and lasting 200 –500 msec after the stimulus. Some of these units also show tonic alteration in rate while a light is shining into one eye. The alteration is either an increase with light to either eye, or a directiondependent increase or decrease, with a latency of 50 –100 msec, and lasting ionically during stimulation times of up to 1 min. The effect is independent of tilt. While the proportion of affected units is small, the elimination of mechanical, muscular, autonomic or antidromic effects and the specificity of many of the responses demonstrate that optic-vestibular integration can involve an efferent control system from the tectum to the otolith organs. The presence of such visual interactions with vestibular input in adult flatfish leads to the hypothesis that the central control of the 90 ° postural change occurring during flatfish metamorphosis may involve crucial optic influences during the period of eye migration.
Maintenance of Constant Wave Parameters by Sperm Flagella at Reduced Frequencies of Beat
Authors: Brokaw C. J. , Josslin R.
Published: April 2021

Treatment of Ciona spermatozoa with low concentrations of Triton X-100 (less than 0·01 %) causes them to beat at lower than normal frequencies. The wavelength of the flagellar bending waves remains constant over the range from 10 to 40 Hz. There is a small increase in wavelength at lower frequencies; in the range of 1·5–6·2 Hz, the wavelength averaged 114% of the normal value for Ciona spermatozoa. The angle of bend of the bent regions of the flagellar bending waves remained constant within ± 10% over this range of frequencies. Decapitated sperm flagella from Lytechinus beat at a continually declining frequency as they exhaust their content of ATP. Both wavelength and bend angle retain normal values until the frequency falls below about 8 Hz. Both parameters increase at lower frequencies, with a sharp increase below 3 Hz. ATP-reactivated spermatozoa from Lytechinus show relatively small changes in wavelength and bend angle as the frequency is varied over the range from 5 to 25 Hz by varying the ATP concentration. Constancy of wavelength over a wide range of frequencies is consistent with the hypothesis that wavelength is determined by the relative values of viscous bending resistance within a flagellum and external viscosity. No satisfactory explanation is available at present for the constancy of bend angle over a wide range of frequencies nor for the changes in wave parameters which are observed at low frequencies.
Studies on Neurohumoral Induction of Compensatory Mechanisms in Thermal Acclimation of Poikilotherms
Authors: Kale Radha D. , Rao Kandula Pampapathi
Published: April 2021

The effect of cold acclimation, which brings about changes in the total metabolism, has been studied in the two species of earthworms Perionyx excavatus and Lampito mauritii. Of the two species the lowest temperature that could be tolerated by Lampito was only 17 ± 1 °C whereas Perionyx could survive at 9 ± 1 °C. The rate of oxygen consumption of the cold-acclimated Perionyx is higher than the rate of respiration of the normal Perionyx when measured at room temperature. The tissue respiration of Perionyx when measured at 20, 25, 30 and 35 °C shows Prosser ‘s acclimation type IV, i.e. translation at lower temperature range and rotation at high temperature. In Lampito the respiratory rate (measured at room temperature) of worms injected with extract of nervous tissue from cold-acclimated worms (18 °C) is higher than that of worms injected with extract of nervous tissue from normal worms. In Perionyx the respiration of the body-wall muscle tissue from injected worms, measured at 20, 25, 30 and 35 °C, is found to be similar to that of the tissues of cold-acclimated worms. It is suggested that the neurosecretions of nervous system have an important role in controlling the metabolic activities during cold-acclimation in earth-worms.
Yolk Protein Synthesis in the Ovary of Octopus Vulgaris and Its Control by the Optic Gland Gonadotropin
Authors: O ‘dor R. K. , Wells M. J.
Published: April 2021

The synthesis of yolk proteins can conveniently be studied in Octopus where removal of the subpedunculate lobe from the brain causes secretion of a gonadotropin by the optic glands and results in precocious sexual maturation (Wells & Wells, 1959). Maturing animals can thus be prepared as needed. The normal reproductive pattern of the female is a further advantage. All the ova from any single animal are deposited during a short period (Mangold-Wirz, 1963) and therefore tend to develop synchronously (Brock, 1879). This results in a high overall rate of yolk synthesis and provides relatively uniform samples of vitellogenic ova without special selection.
Experimental Disruption of the Blood-Brain Barrier System in An Insect (Periplaneta Americana)
Authors: Treherne J. E. , Schofield P. K. , Lane N. J.
Published: April 2021

The effects of hypertonic urea and hypertonic glucose solutions upon the ‘blood-brain barrier’ in the isolated abdominal nerve cord of the cockroach have been studied. Electrophysiological studies showed that a hypertonic solution of urea, but not of glucose, was effective in reducing the barrier to the entry of potassium and the loss of sodium. Electron-microscopic studies revealed no significant ultrastructural changes, and no disruption of the perineurial barrier to the entry of ionic lanthanum, following comparable exposure to the hypertonic solutions. It is suggested that this alteration of the blood-brain barrier may result from a selective change in permeability of the perineurial membranes or tight junctions.
Wall Drag On Free-Moving Ciliated Micro-Organisms
Authors: Winet H.
Published: April 2021

It is generally assumed that wall drag on free-moving, self-propelled or passively moving micro-organisms is not significant under normal observation conditions. Yet the point at which such drag becomes significant has not been determined quantitatively.

By comparing the relative velocities of sinking as well as swimming ciliates in tubes of various bore widths it has been determined that wall drag on sinking cells is about 8 % significant at 10–132 body radii (or minor semi-axes) from the cell surface while the corresponding range for swimming cells is less than 1–4·2 body radii.

These results are compared with the mathematical approximations for Stokes radius Rs and depth of penetration of diffusing vorticity δ which characterize steady and quasi-steady Stokes flow respectively around a solid body. It is found that the asymptotic nature of the velocity profile of steady flow is reflected in the lack of agreement between Rs and the measured distance for 8 % drag. Conversely, the sharp gradient (or propulsive envelope) of the quasi-steady velocity profile is reflected in the substantial agreement between 8 and the measured distance for > 0 % drag.

It is suggested that the given formula for 8 which includes allowance for a propagated wave is a valid measure of the thickness of the quasi-steady region and that observations on motile ciliates be restricted to organisms at least 4 cell radii from the nearest wall if measurements free of wall-drag effects are to be obtained.
On Ligature of the Vas Deferens in the Cat and Researches on the Efferent Ducts of the Testis in Cat, Rat and Mouse
Authors: Cunningham J. T.
Published: April 2021

In a previous paper, June 1927, I described and discussed experiments on artificial cryptorchidism and ligature of the vas deferens in rabbits. The present paper deals with one experiment on ligature of the vas deferens in the cat and several experiments on ligature of the vasa efferentia in the rat, together with a microscopic investigation of the origin, course and structure of those ducts and of the successive parts of the epididymal tube.
The Rôle of Water in the Evolution of the Terrestrial Vertebrates
Authors: Gray J.
Published: April 2021

The origin of truly terrestrial vertebrates was associated with the development of a skin which is relatively impermeable to water. The skins of fishes and of most amphibia are freely permeable to water, and water is readily lost when the animals are exposed to ordinary atmospheric conditions. The skin of a lizard on the other hand is relatively impermeable to water and the animal is therefore able to withstand exposure to air without serious inconvenience. Complete adaptation to terrestrial conditions involved the capability of laying and incubating eggs on land. The eggs of fish and of typical amphibia absorb, during development, considerable quantities of water from the external environment. The embryos of reptiles and of birds derive the equivalent of this water from the albumen layer secreted round the ova by the walls of the oviduct. Evidence is presented to show that the reptilian type of egg is to be derived from that of a dipnoan or amphibian, where the egg is surrounded by a mucilaginous or albuminous secretion of the walls of the oviduct. The mammalian egg can be derived from that of a reptile by supposing that the aqueous secretions of the oviduct are passed direct into the embryo instead of forming a separate phase round the ovum. An intermediate type is found in Monotremes where the secretions are passed into the ovum itself before the egg is laid.
An Experimental Examination of the Evidence for the Presence of Phosphatides in the Limiting Surface of the Living Protoplast
Authors: Steward Frederick Campion
Published: April 2021

An outstanding problem of plant physiology is the nature of the mechanism which controls the movement of water-soluble substances into, and out of, the living cell. Recent investigations confirm the long established impression that in the vacuolar sap of living cells substances are present, which, although soluble in water, are almost unable to diffuse out when the cell is surrounded by water. It is clear that the living protoplast is responsible for this, since complete permeability is associated with death. Moreover, it is well established that the degree of permeability of living cells to solutes is dependent upon the composition of the medium with which they are in contact, and its consequent effect upon the plasma surface. Leaving on one side the controversy concerning the existence and constitution of a specific plasma membrane, which may be. responsible for these attributes of living cells, it is clear that the phenomena associated with boundary phases give adequate grounds for anticipating that the external surface of the protoplast will have a different composition from the main protoplasmic mass. It is natural that the composition of this surface layer should be stressed in theories of cell permeability, but it is clearly undesirable that our knowledge of its nature should rest largely on speculation.
On the Fixation of Atmospheric Nitrogen by Phoma Radicis Callunae, Including A New Method for Investigating Nitrogen-Fixation in Micro-Organisms
Authors: Jones W. Neilson , Smith M. Llewellyn
Published: April 2021

(1) Evidence from chemical analyses of seeds of Calluna mdgaris and of seedlings grown on a nitrogen-free medium confirms the view that this plant can obtain nitrogenous supplies from the air, probably in the form of molecular nitrogen, in sufficient amount to prevent the advent of any symptoms of nitrogen starvation. (2) A new apparatus for the investigation of nitrogen-fixation by micro-organisms is described. (3) Using the above apparatus, experiments on the mycorrhizal fungus of Calluna vulgaris are described in which this organism was grown in pure culture on a nitrogen-free medium with and without a supply of molecular nitrogen. The evidence obtained indicates that the amount of glucose used by the fungus during growth, and the amount of nitrogen contained in the culture at the end of the growth period are greater under the former condition. It is concluded that the fungus in question can utilise the molecular nitrogen of the air in some degree under the conditions of the experiments, although these were not the most favourable possible for nitrogen-fixation.

It is considered that the results obtained justify an extension of these experiments using a strain of the fungus freshly extracted from the Calluna plant.
Rhythmic Susceptibility Changes in the Cleaving Arbacia Egg
Authors: Page Irvine H.
Published: April 2021

The fertilisation reaction initiates a remarkable series of events in the egg. Lyon(1) first showed that Arbacia eggs were especially sensitive to heat just before cleavage and most resistant 10–20 minutes after fertilisation. However, the susceptible period for cold seemed to be quite different from that for heat, being almost exactly the same as the resistant period for heat. He (2) further found that eggs were especially susceptible to M/100-M/200 KCN about 10–15 minutes after fertilisation and that the resistance gradually rose as the time for the first cleavage approached.
Temperature and Heart-Rate in Fundulus Embryos
Authors: Glaser Otto
Published: April 2021

On the 4th day after fertilisation, cardiac rhythm in Fundulus embryos, in all probability, is myogenic. Between 5 ° and 25 ° C., one of two temperature characteristics prevail and fluctuate either about μ = 16,300 or 14,300. On the 12th day, embryos, presumably neurogenic, expose prevailing increments of 20,900 or occasionally of 18,200. A definite critical region is localised about 20 ° where the prevailing increments break to the orders 16,000, 14,000 or 12,000. Over the corresponding range embryos about to escape from the egg-case, exhibit, in the only two instances recorded, μ = 23,000, 20,900 and 16,300. On presumable restoration of myogenic conditions in embryos of the 12th day, μ may be 14,300 over the entire range. The frequency of μ = 14,300 is greater than in normal larvae of the same age, whereas μ = 20,900 is restricted to the lower temperatures. In their bearing on the differences between myogenic and neurogenic rhythms, these results become explicable if we imagine an underlying mechanism identical for both cases. The same increments either occur or suggest themselves at all stages of development, or, if at times some appear to be distinctive of neurogenic Fundulus, these can be promptly duplicated from the list of increments shown by myogenic Limulus, e.g. 20,900. Clearly, however, the most frequent characteristics found belong to categories exposed by a great variety of biological acts, and their association in cardiac rhythms is common. These two facts harmonise well with the recent work on the metabolism of muscle and nerve.
The Significance of the Bohr Effect in the Respiration and Asphyxiation of the Squid, Loligo Pealei
Authors: Redfield Alfred C. , Goodkind Robert
Published: April 2021

In 1904 Bohr, Hasselbalch and Krogh showed that carbon dioxide diminished the affinity of haemoglobin for oxygen. This phenomenon, known as the “Bohr effect,” together with the reciprocal effect of oxygenation upon the combination of carbon dioxide with blood, discovered by Christiansen, Douglas and Haldane (1914) must be taken into account in all quantitative considerations of the respiratory function of the blood of mammals. It is now recognised that the effects of carbon dioxide are not specific, but are due to alterations in the acid-base equilibrium of the blood and may be produced by other acids. The phenomena have also been described in the case of the blood of the lower orders of vertebrates (Krogh and Leitch, 1919; and Southworth and Redfield, 1926) and of the body fluids of invertebrate animals, such as the worms which have respiratory pigments more or less closely related to haemoglobin (Barcroft and Barcroft, 1924).
The Effect of Testicular Extracts on the Blood Calcium
Authors: Mirvish L. , Bosman L. P.
Published: April 2021

It has long been recognised that the testis has an influence upon growth in general, and especially upon the growth of bone. This was the basis for the generalisation formulated by the early observers that growth and reproduction are essentially opposed to one another. Later investigations indicated, however, that the changes produced by castration are not due to the abolishing of spermatogenesis but to the fact that the normal internal secretion of the testis is not available for controlling the growth of bone.
The Metabolic Gradient and its Applications
Authors: Parker G. H.
Published: April 2021

In Nereis virens the rate of carbon dioxide discharge for the whole worm is roughly o ·01 milligram of gas per gram of worm per minute. In similar terms the rate for the mid-trunk is a little over 0 ·01 milligrams and that for the head and tail regions about half of this rate. In Planaria maculata large worms (87 mgm.) show a lower rate of carbon dioxide discharge (0 ·0050 mgm. per gram of worm per minute) than small ones (55 mgm.) (0 ·0069 mgm. per gram of worm per minute). Also normal worms have a lower rate (0 ·0050 mgm.) than cut worms (0 ·0063 mgm.). Planarians cut transversely into halves, quarters or sixths show in such fragments so uniform a rate of carbon dioxide discharge that there is no reason to believe that the rate is really different in different parts. In the actinians Sagartia luciae and Metridium marginatum the rate of discharge of the oral halves is indistinguishable from that of the aboral halves and these two rates are very close to the rates of the animals as wholes. These results point to the absence of the assumed metabolic gradients in Nereis, Planaria and the actinians. Hyman’s results on annelids with the susceptibility method were obtained on Nereis but are believed to be due to differential penetration and are not accepted as a proof of a metabolic gradient. Hyman and Galigher’s results on annelids involve a misuse of the Winkler method. Shearer’s results on earthworms apply only to the head and tail ends and should have been supplemented, to be conclusive, with determinations for the mid-trunk. Metabolic gradients if present are not factors in morphogenesis but are at best measures of activity which may serve as features in the description of organisms.
The Anatomy of A Locust Visual Interneurone; the Descending Contralateral Movement Detector
Authors: O ‘shea M. , Rowell C. H. F. , Williams J. L. D.
Published: April 2021

The DCMD neurone is physiologically well-known and runs from the brain to the metathoracic ganglion. It responds to novel movement of small contrasting objects in the visual field and synapses on metathoracic motoneurones which mediate the jump of the locust. Its anatomy, here reported, has been visualized by intracellular cobalt staining. The soma is 50μm in diameter and lies on the upper posterior face of the protocerebrum, lateral to the midline. A neurite runs to a thickened integrating segment 20 μm in diameter, which bears numerous dendrites ; none of these extends to the optic lobe. An axon leaves the integrating segment, crosses the brain, thickens to about 17 μm and descends the contralateral nerve cord. The descending axon terminates in the metathoracic ganglion, where it has three major branches both ipsi-and contralateral. Its branching in the mesothoracic ganglion is similar, but extends only ipsilaterally; in the prothoracic ganglion there is reduced branching, and in the suboesophageal ganglion none at all. The branching pattern in the metathorax is compatible with, and entirely explicable by, the known synaptic connexions with motoneurones. The morphological description of the cell has made possible intracellular recording from axon, integrating segment and soma.
Command Fibres in the Circumoesophageal Connectives of Crayfish
Authors: Bowerman R. F. , Larimer J. L.
Published: April 2021

Command interneurons from the circumoesophageal connectives of crayfish which are capable of evoking various cyclical, phasic behavioural outputs are described. By pooling evoked-behaviour data and information on command-fibre location for a number of preparations it has been possible to repeatedly identify certain individual interneurons. Five escape or swimming-command identities have been established. Electrical stimulation of any of these elements activates the fast abdominal musculature, generating single or multiple tail-flips. Three forward-walking identities have been established within the experimental connective. Stimulation of a forward-walking command fibre results in extension of the abdomen and chelipeds in conjunction with locomotory movements of the walking legs. Output has been characterized as walking by virtue of the fact that the walking wheel is actually rotated by the stepping appendages. Four backward-walking identities have been established. For these command elements a variety of cheliped and abdominal geometries are superimposed on the basic backward-stepping patterns of the walking legs. Cyclical command fibres capable of evoking branchiostegite scratching, feeding-Fike activity, cleaning of the dorsal aspect of the abdomen, and slow rocking of appendages have also been noted.
A Study of the Malpighian Tubules of the Pill Millipede, Glomeris Marginata (Villers)
Authors: Farquharson Patricia Anne
Published: April 2021

The Malphigian tubules of the pill millipede, Glomeris marginata are described. After the necessary analyses of the haemolymph had been carried out a Ringer solution was prepared which would support the secretion of tubule fluid in vitro. The reasons for the variation and deterioration in the secretion rates of control tubules are discussed. The presence of various amino acids in the bathing medium appears to be essential for fluid production. There would not appear to be a diuretic hormone involved in the control of secretion; and 5-HT, cylic AMP and theophylline will not stimulate fluid production. Secretion is inhibited by the metabolic inhibitors 2,4-DNP, azide and cyanide. The relative insensitivity shown to the latter two compounds is probably associated with a resistance mechanism.
Theory of CO2 Exchange in Trout Gills*
Authors: Cameron James N. , Polhemus John A.
Published: April 2021

A computer simulation of countercurrent CO2 exchange in fish gills was constructed to examine effects of variations in blood and water flow rates. CO2 output was sensitive to both blood and water flow rates, contrary to experimental data. Various explanations of the contradiction are discussed, including patterns of gill perfusion and possible shunting of blood. A simplified version of the model was also used to demonstrate extreme sensitivity of COS efflux to variations of the residence time of blood in the gills. Data from the literature on reaction rate constants for the CO2/carbonate/ bicarbonate system are summarized, and the importance of some of these reactions is examined.
Analysis of the Electrophysiological Responses of the Trochanteral Hair Receptors of the Cockroach
Authors: Spencer H. J.
Published: April 2021

In arthropods much of the body surface bears innervated hairs or bristles which have the general histological structure described by Snodgrass (1935) as sensilla trichoidea, and it is generally assumed from their positions that they are either mechanoreceptors or chemoreceptors. A number of studies have shown that tricho sensilla of similar histological structure respond to very different sensory modalities and that to some extent the receptor response spectrum is determined partly by the structure of the hair and partly by the characteristics of the innervating neurone (Dethier, 1963).