bluuebunny/crossref_metadata_2025 huggingface dataset:
An Electrophysiological Study of Neuroglandular Transmission in the Isolated Salivary Glands of the Cockroach
Authors: House C. R.
Published: April 2021

Some aspects of neuroglandular transmission in isolated salivary glands of the cockroach have been studied. The membrane potential of acinar cells is – 32 ·3 ±0 ·8mV (mean ±S..E; N = 600 cells) when the gland is bathed in Ringer solution. Upon delivering a single shock by ‘field stimulation’ to the salivary nerves the gland cell membrane undergoes after an initial latency of 1 second a transient hyperpolarization of about 1 –30 mV which lasts for about 10 sec. When the salivary nerves are stimulated by trains of current pulses the hyperpolarization that occurs is larger in amplitude and longer in duration than that after a single stimulus. The amplitude of the responses to single shocks and stimulus trains depends on the external potassium concentration. Thus, the neurotransmitter may increase membrane permeability to potassium ions. The electrical response of the gland cell to 5-hydroxytryptamine in concentrations from 2 ·5 –250 × 10 −7M is similar in sign and magnitude to that of nervous stimulation. Occasionally small fluctuations in the membrane potential are observed and these are similar in sign and duration to responses elicited by single shocks to the salivary nerves.
The Mechanism of Rapid Running in the Ghost Crab, Ocypode Ceratophthalma
Authors: Burrows Malcolm , Hoyle Graham
Published: April 2021

Ocypode ceratophthalma has a maximum speed of 2·1 m/sec when running on a measured track with a base of hard-packed sand. Speed increases linearly with the width of the carapace up to a certain size, beyond which larger crabs run slower than smaller ones. The crab does not run at these high speeds by making extremely rapid movements as these data seemed to require. The highest frequency of leg movements observed was 20 Hz. Electromyographs of muscles used in running, made from the freely running, intact crab, showed asymmetry in the motoneurone discharges. Extensors and flexors in the meropodites of legs on the leading side frequently showed only a maintained tonus and could not have contributed to the running movements. Those on the trailing side showed alternation synchronous with stepping. It is concluded that the crab mainly pushes itself along rather than using a push-pull combination. Three pairs of legs are commonly used in running. Legs 2 and 4 of one side move together with leg 3 of the opposite side and provide a tripod of support. At the highest speeds only legs 2 and 3 of one side are used to provide thrust alternately. The high speed is achieved by the crab leaping through the air as it steps, thereby increasing the effective length of the steps.
The Mechanics of the Growing Semicircular Canal
Authors: Kate J. H. Ten
Published: April 2021

The motion of the endolymph in the semicircular canal is described with the aid of a linear second-order system, comprising the applied angular acceleration and the linear displacement, the linear velocity and the linear acceleration of the endolymph. A sensitivity factor G for angular velocity is derived and expressed in the dimensions of the semicircular canal. The sensitivity factor G of the semicircular canal proves to be consistent with the equivalent sensitivity factor of a more sophisticated hydrodynamic model of these canals. The sensitivity of the growing semicircular canal is defined to be , independent of the pike’s size. Threshold angular velocities for the vestibulo-ocular reflex of 27 pike between 4 and 50 cm bodylength are in agreement with this assumption. At threshold stimulation with an angular velocity of 2°/sec the radius of curvature Rc of the cupula is calculated to be 220 ± 48 cm. At the threshold angular velocity γ = 2°/sec the deviation of sensory hairs 5 μ m long is assessed to be between 0·06 Å and 1 Å. Young’s modulus of elasticity for the cupular substance is found to be between 0·35 × 103 dyne/cm2 and 1·85 × 108 dyne/cm2 (on the basis of a circular bending for the cupula). Characteristics of the model of the growing semicircular canal are calculated for pike with body length between 5 and 100 cm. Observed growth effects of the pike’s vestibulo-ocular reflex arc are correlated to the growth effects calculated on basis of the model for the growing semicircular canal. The pike possesses the same degree of vestibulo-ocular compensation in the high-frequency range (2 radians/sec = ⩽ ω< 7 radians/sec) of angular oscillations during its whole life (11 observations of pike of body length 4–56 cm).
The Role of Calcium in the Action of 5-Hydroxytryptamine and Cyclic Amp on Salivary Glands
Authors: Prince William T. , Berridge Michael J.
Published: April 2021

The role of calcium in the potential and secretory responses of isolated salivary glands of Calliphora to 5-HT and cyclic AMP has been studied. Secretion induced by 5-HT was reversibly inhibited by removal of calcium from the bathing medium. The chloride-dependent depolarization of the apical membrane produced by 5-HT was calcium dependent whereas the potential response to cyclic AMP was little effected. Strontium and barium effectively substituted for calcium. Manganese replaced calcium at the onset of secretory and potential responses but these responses were maintained when manganese was removed. Lanthanum did not substitute for calcium in secretory responses but did inhibit the secretory and potential responses to calcium in calcium-depleted glands. The rate of secretion in a low-chloride medium produced by cyclic AMP was significantly lower than that induced by 5-HT, but there was little difference in normal saline. A model for the mode of action of 5-HT is proposed in which calcium acts as an intracellular intermediary controlling chloride movements whilst cyclic AMP controls a potassium pump.
Progressive Decrements in the Activity of Aplysia Neurones Following Repeated Intracellular Stimulation: Implications for Habituation
Authors: Stephens Cathy Lamar
Published: April 2021

Repeated intracellular stimulation of nuerones from the isolated abdominal ganglion of Aplysia californica produced progressive response decrements with parametric features common to trans-synaptic models of habituation. The probability that a constant intracellular pulse of depolarizing current would produce an action potential decreased with repeated stimulation, the response decrements developed with interstimulus intervals ranging from 2 to 10 sec. In all cases, the response decrements were reversible with prolonged rest. In some cases complete recovery did not occur for up to 20 min, which indicated that the spontaneous recovery process was long-term in nature. As is typical of parametric studies of habituation, short, rather than long interstimulus intervals, and a weak, rather than a strong stimulus, produced greater response decrements. These results demonstrate that an individual neurone shows response decrements as a function of repeated stimulation, which suggests that there are at least two processes responsible for the response decrements seen during trans-synaptic stimulation: (a) synaptic depression and (b) a depressive process originating in the post-synaptic neurone.
Properties of Stalk-‘Muscle’ Contractions of Carchesium Sp.
Authors: Rahat M. , Pri-Paz Y. , Parnas I.
Published: April 2021

The stalk of Carchesium was found to contract in an ‘all or none’ fashion in response to electrical stimuli. Rise time and half-decay time of contractions were 40−60 msec and 800−900 msec respectively. Forces developed during contraction were between 400−800 g/cm2. At o·2 stimuli/sec or less, the stalk contracted at a one-to-one ratio. At higher rates of stimuli the stalk contracted at its own pace, indicating an intrinsic refractory system. No tetanic responses or summation were observed in normal stalks. In fatigued stalks, partial summation was obtained and relaxation time was increased. It is concluded that the contractile system of Carchesium is probably different from that of a metazoan muscle.
Impulse Activity and Pattern of Large and Small Neurones in the Cardiac Ganglion of the Lobster, Panulirus Japonicus
Authors: Tazaki Kenro
Published: April 2021

The cardiac ganglion of the lobster, which contains five large and four small cells (Alexandrowicz, 1932), produces integrated patterns of burst discharges. Maynard (1955, 1966) described how this ganglion may be compared to a miniature central nervous system, and pointed out that integrative processes occurring within the ganglion are of great interest because analyses of a simple nervous system may be an approach to the study of integration in complex nervous systems. Electrophysiological investigations of these ganglion cells have been reviewed by Hagiwara (1961). Intracellular studies have been made in detail on large cells of Panulirus (Hagiwara & Bullock, 1957; Bullock & Terzuolo, 1957; Watanabe, 1958; Otani & Bullock, 1959; Hagiwara, Watanabe & Saito, 1959; Watanabe & Bullock, 1960; Tazaki, 1971b, 1972a). The conclusion concerning their activity is as follows: large cells (followers) are innervated by common presynaptic nerve fibres from small cells (pacemakers), and potential changes during the burst are several kinds of synaptic potentials and spikes. This conclusion is not, however, valid for the Homarus ganglion. Cooke (1966) and Connor (1969) have studied the intracellular activity of its large cells. Connor (1969) has concluded that potential deflexions are due toendogenous activity of the respective neurones and not to synaptic potentials.
Branchial Sodium Transport Mechanisms in Scyliorhinus Canicula: Evidence for Na+/NH4+ And Na+ H+ Exchanges and for A Role of Carbonic Anhydrase
Authors: Payan P. , Maetz J.
Published: April 2021

Smith (1953) suggested that during the course of evolution, the transition between invertebrates and vertebrates occurred in the marine environment at the beginning of the paleozoic era. Much later, during the Silurian period, the hypothetical ‘Protovertebrates’ invaded brackish and fresh waters. In these media it is probable that their body fluids remained hyperosmotic to the external medium, although their osmolarity must have declined to a certain extent.
Effects of Ambient Temperature on Warm-Up in the Moth Hyalophora Cecropia
Authors: Bartholomew George A. , Casey Timothy M.
Published: April 2021

The rates of pre-ffight warm-up in adult Hyalophora cecropia (mean weight 3·10 g) were measured 24−36 h after eclosion at 15, 20, 25, and 30 °C in still air.

The rate of thoracic warm-up increased linearly with ambient temperature, averaging 2.6 °C/min at 15 °C and 6.5 °C/min at 30 °C. Thoracic temperatures typically reached 37−39 °C while abdominal temperatures rarely rose more than 3 °C above ambient. The cooling curves of the thorax at 15°and 25°C were straight lines and had similar slopes on a semi-logarithmic plot. Our data are compatible with the idea that heat production is dependent on thoracic temperature, and are incompatible with the theory that it depends on the difference between thoracic and ambient temperatures.
Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni
Authors: Kaufman W. R. , Phillips J. E.
Published: April 2021

An in vitro method is described for stimulating the salivary gland of Dermacentor andersoni to secrete fluid. In vitro glands require the presence of a catecholamine for salivation to occur. Natural haemolymph from salivating ticks does not trigger secretion suggesting that the tick does not produce a‘salivation hormone’ analogous to the diuretic hormones of certain insects. Pilocarpine, glutamate and malate did not stimulate secretion in vitro. Isoproterenol and 5-hydroxytryptamine were relatively weak stimulants (threshold concentrations of approximately 10−5 M and greater than 10−4 M respectively). Adrenaline, noradrenaline and dopamine were highly effective stimulants, the threshold concentrations being no more than 10−6 M. Adrenaline could also elicit a copious secretion in vivo at a final haemocoele concentration of about 2 × 10−5 M. We postulate that salivation occurs by means of a secretory rather than a filtration-resorption mechanism. Control of fluid secretion is probably neural rather than hormonal, the transmitter substance being a catecholaminergic substance.
Bird Metabolism During Flight: Evaluation of A Theory
Authors: Tucker Vance A.
Published: April 2021

Pennycuick’s (1969) theory for the energetic requirements of avian flight predicts the metabolic rates of budgerigars and laughing gulls flying level at intermediate speeds in a wind tunnel with an accuracy of 10% or better. However, its predictions appear to be low for most birds with masses less than 0·1 kg and high for most birds with masses greater than 0·5 kg. Four modifications are made to Pennycuick’s theory : (1) a different computation of induced power; (2) a different estimate of equivalent flat plate area that includes Reynolds number effects, and is based on additional measurements; (3) a different estimate of profile power that includes Reynolds number effects; and (4) the addition of power terms for respiration and circulation. These modifications improve the agreement between the theoretical predictions and existing measurements for flying birds and bats. The metabolic rates of birds and bats in level flight at various speeds can be estimated by the modified theory if body mass alone is measured. Improved estimates can be made if wing span is measured as well. In the latter case the theory predicts measured values with a mean absolute error of 8·3 %. The results of the modified theory are presented by approximate equations that can be solved quickly for metabolic rate and flight speed with a slide rule.
Mechanism of the Spermatophoric Reaction in the Giant Octopus of the North Pacific, Octopus Dofleini Martini
Authors: Hanson D. , Mann T. , Martin A. W.
Published: April 2021

The spermatophoric reaction in the giant octopus requires 1-2 h, and during that time the large mass of spermatozoa contained in the proximal (male-oriented) portion of the spermatophore, is propelled over a metre-long distance to the distal (female-oriented) end. Osmotic pressure provides the main mechanism for the spermatophoric reaction; and the influx of sea water, as a result of which the intraspermatophoric fluid space increases fivefold, provides the main force for driving the spermatozoa from the proximal to the distal end of the spermatophore. The outer tunic of the spermatophore acts as a semipermeable membrane, permeable to sea water but not to macromolecular substances. Its strength is adequate to resist inside pressure 400 cm water in excess of the external environment. In the normal course of spermatophoric reaction intraspermatophoric hydrostatic pressure increases from about 140 cm water at the onset of the reaction to about 330 cm H2O at the moment when the cap of the spermatophore ruptures and the ejaculatory apparatus is extruded; the rate at which pressure increases during this phase of the reaction is about 8 cm H2O/min. Immediately after the extrusion of the ejaculatory apparatus the pressure falls precipitously. It then increases once more, but very slowly, reaching 45–95 cm H2O before the ejaculatory apparatus evaginates. It declines once more during the final stage of the evagination process. At the end of the spermatophoric reaction the transmural pressure is only about 9 cm H2O in the spermatophoric bladder but approximately 4 times higher in the proximal portion of the spermatophore.’ In spite of the increase in the concentration of sodium and chloride ions in the intraspermatophoric fluid, the osmolality of that fluid remains largely unaltered throughout the whole spermatophoric reaction, but always at a level distinctly higher than the surrounding water (by about 30 mOsm/kg water). Large-molecular glycoproteins in the spermatophoric plasma are probably undergoing enzymic breakdown by glycosidases during the spermatophoric reaction, as a result of which some carbohydrate, aminosugar and other nitrogenous organic material pass from the interior to the exterior of the spermatophore.
Acoustic Properties of the Cod Swimbladder
Authors: Sand Olav , Hawkins A. D.
Published: April 2021

The resonance frequency and damping of the swimbladder were measured for intact living cod at different depths. At adaptation depth, the resonance frequency (fr) of the organ was much higher than that predicted for an unrestrained gas bubble of similar volume. However, at much greater depths (where the hydrostatic pressure was 2 or more times greater than the adaptation pressure) fr was only higher than expected by a factor of 1 · 25, and changed with depth in the manner of a free gas bubble. The elevated values at greater depths can be explained in terms of the difference in shape between the swimbladder and an ideal spherical bubble, together with a light effect from the surrounding tissues. We have calculated that the shear modulus of these tissues (μ1) has a value of approximately 1 · 7 × 106 dyne/cm2. However, we have suggested that the much higher elevation of fr found at the adaptation depth results from a large increase in μ1(by a factor of between 6 and 120). This increase may be the result of a maintained muscle tonus. There is an immediate drop in fr as a fish is moved to a new depth, but the elevated values are rapidly restored with time. This process of adjustment is too rapid to be accounted for by the restoration of the swimbladder to its former volume by the secretion or absorption of gas. It is possible that it is achieved by a muscular mechanism which restores μ1 to the former high value. Though the maintenance of fr at a high value may reflect mechanical processes concerned with the hydrostatic function of the swimbladder, or with the detection of static pressure changes, we suggest that it may also be of some value if the swimbladder is used as an accessory hearing organ. The maintenance of an fr well above the hearing range of the fish ensures that the relative sensitivity of the animal to different frequencies does not alter with changes in depth.
Physiology of Insect Ecdysis
Authors: Truman James W.
Published: April 2021

Ecdysis of insects involves a series of behavioural and physiological processes which are concerned with the escape of the insect from the confining exuviae and the expansion and tanning of the new cuticle. Cottrell (1962a, b) and Fraenkel & Hsiao (1962) first reported that a blood-borne factor triggered the tanning of the cuticle of the newly emerged fly. This hormone, which was later termed bursicon (Fraenkel & Hsiao, 1965), is released after the newly emerged fly has dug its way out of the soil. In other insects bursicon secretion is more closely associated with ecdysis and occurs slightly before or during the shedding of the old skin (Cottrell, 1962 b;Fraenkel & Hsiao, 1965; Mills, Mathur & Guerra, 1965).
Spatial and Temporal Changes in the Coupling of Cockroach Spiracles to Ventilation
Authors: Miller P. L.
Published: April 2021

Spiracles 10 of Blaberus giganteus can be coupled with ventilation so as to open either with inspiration or with expiration. Similar activity in a mantid has been shown to produce either anteriorly or posteriorly directed ventilating airstreams in longitudinal tracheae. Switching between the two modes of coupling, which can be controlled experimentally, may pass through a maintained transitional stage when both forms occur. Coupling with inspiration involves symmetrical activity in opener muscles of left and right spiracles. However, when coupled to expiration only one spiracle is active. The unilateral application of electrical or mechanical stimuli to various regions of the body causes the spiracle on that side to open with expiration. Medially divided abdominal ganglia still joined to the CNS through the connectives are capable of both forms of coupling. It is suggested therefore that reciprocal inhibitory coupling between coordinating intemeurones and not between motor neurones accounts for asymmetrical activity when the spiracles are coupled to expiration. Spiracles 3, 6, 7 and 8 act in a similar way to spiracle 10 but have higher thresholds. Spiracles 4, 5 and 9 are associated with glandular structures and their activity is different. They may allow chemicals to be expelled through them when the insect is strongly stimulated. A model is presented which accounts for some aspects of the activity of spiracles 10.
Neuro-Muscular Mechanisms of Abdominal Pumping in the Locust
Authors: Lewis G. W. , Miller P. L. , Mills P. S.
Published: April 2021

The muscles involved in dorso-ventral and longitudinal ventilation in the pregenital segments of Schistocerca gregaria are described. Expiratory muscles are shown to be innervated by paired lateral nerves whereas the dorso-ventral inspiratory muscles are innervated by the unpaired median nerve system. Normal pumping activity is brought about by alternating bursts of impulses in expiratory and inspiratory motor nerves. Inspiratory bursts are relatively invariant, whereas expiratory bursts show a positive correlation with ventilatory cycle length. The firing patterns of some units within the bursts are described. In general anterior segments fire motor bursts earlier than posterior segments during well synchronized active ventilation, the metathoracic ganglion firing first. However, much variation is seen both within one locust and between different locusts. Burst-formation continues in isolated nerve cords. Activity, phase-locked with expiration, has been recorded in the connectives. The evidence suggests that it occurs in a pair of co-ordinating interneurones which run from the metathoracic ganglion to the last abdominal ganglion and determine the initiation, duration and possibly the intensity of the expiratory motor bursts in each segment. A second parallel system may co-ordinate activity when the metathoracic co-ordinating interneurones are inactive. Inspiratory motor neurones are probably autoactive and the duration of their firing may normally be determined by the discharge phase of a metathoracic oscillator which acts by inhibiting the co-ordinating interneurones.
The Respiratory Physiology of the Marine Nematodes Enoplus Brevis (Bastian) and E. Communis (Bastian)
Authors: Atkinson H. J.
Published: April 2021

The rate of oxygen consumption of individual male Enoplus brevis and E. communis was measured at 15 °C, after altering the oxygen regime experienced since the animals were collected. When both E. brevis and E. communis were transferred to 35 Torr from atmospheric oxygen tensions, their oxygen consumption was only two-thirds of that of individuals maintained at this lower oxygen tension. The rate of oxygen consumption of the two species at 135 Torr was unaltered by exposure for 2 h to oxygen-free sea water. The results are discussed in relation to the overall influence of fluctuating oxygen regimes on the oxygen requirements of nematodes.
Sensory Mechanisms in Paramecium
Authors: Naitoh Yutaka , Eckert Roger
Published: April 2021

Small, brief mechanical stimuli were delivered with a microstylus to the surface of Paramecium caudatum bathed in solutions of 1 mM-CaCl2, 1 mM KC1 +1 mM Tris HC1, pH 7 2. Stimulation of the caudal end produced a graded hyperpolarizing receptor potential which reached a maximum within 50 msec and decayed more slowly. The input conductance at the peak of the caudal receptor potential increased to a value of at least 6 times that of the resting membrane. The potential diminished in amplitude when the membrane was hyperpolarized by injected d.c. current, and reversed sign with sufficient hyperpolarization. The reversal potential in a solution of 1 mM-CaCl2 + 4 mM-KCl was − 37 mV, while the resting potential was − 20 mV. The peak of the receptor potential was shifted about + 50 mV per 10-fold increase in extracellular K+. C−and Ca2+ and other cations produced little or no shift in the potential peak of the response. It is concluded that mechanical stimulation of the caudal surface produces a local increase in conductance, predominantly to K+. Extracellular tetraethylammonium converts the normally hyperpolarizing receptor potential to a depolarization similar to the potential produced in response to mechanical stimulation of the anterior surface. The TEA effect is antagonized by calcium ions.
Some Evidence for Colour-Blindness in Octopus
Authors: Messenger J. B. , Wilson A. P. , Hedge A.
Published: April 2021

Groups of O. vulgaris were trained successively to make brightness and hue discriminations with painted vertical rectangles. These were of approximately the same physical intensity and were equally preferred. Using one-cue discrimination training we found that (a) Seven octopuses that discriminated between dark blue and light blue did not discriminate between dark blue and dark red shapes. (b) Nine octopuses that discriminated between light red and black did not discriminate between light red and light green shapes, (c) Fifteen octopuses that discriminated between medium green and light green did not discriminate between medium green and medium blue shapes. All these octopuses later discriminated between black and white shapes. Another group of octopuses was trained with two cues, one or both of which were relevant. The cues used were brightness (dark or light) and hue (blue or green), (a) Group 1 (N =14) discriminated between dark and light shapes where hue was irrelevant. (b) Group 2 (N = 14) discriminated between dark blue and light green shapes, (c) Group 3 (N =14) failed to discriminate between blue and green shapes where brightness was irrelevant. Overall the scores of Groups 1 and 2 did not differ significantly. Thus under experimental conditions where octopuses rapidly learned to make brightness discriminations they did not learn discriminations based on hue alone; even if colour is perceived, it seems a relatively unimportant cue for this animal. Another group of octopuses (N = 10) was tested, in a special apparatus, for nystagmus and optomotor responses. Such responses were always given when stripes of different brightness moved relative to the retina, but when stripes of the same subjective brightness but different hue moved across the eyes they rarely occurred. Such occurrences were no more frequent than the responses given to a plain grey background. Similar results were obtained under conditions of illumination ranging from less than 1 lux to 7·5 × 104 lux. The absence of visual response to moving coloured stripes suggests that the failure of octopuses to learn a hue discrimination may be the result of an inherent incapacity at the retinal level. Together with other findings, which are discussed, this strongly suggests that O. vulgaris is colour-blind.
The Circulatory Physiology of Helix Pomatia: III. The Hydrostatic Pressure Changes in the Circulatory System of Living Helix
Authors: Sommerville Barbara A.
Published: April 2021

The pressure changes in the mantle cavity and various parts of the circulatory system of Helix pomatia have been measured. There are characteristic pressure changes associated with the breathing movements, the pattern depending upon the point at which the measurement was made and, in the case of the heart, the position of the body at the time of recording. These pressure changes fall mainly within the range 2–8 cm H2O. The pressure changes associated with contraction of the heart chambers fall within the range 1–2 cm H20 in pulmonary vein and auricle, 10–32 cm H20 in the ventricle, 1–3 cm H2O in the aorta and 1–8 cm H2O in the pericardial cavity. An increased frequency and amplitude of heart beat was associated with an increased rate of blood flow.
Central Control of Postural Orientation in Flatfish
Authors: Platt Christopher
Published: April 2021

Flatfish metamorphose from a larval form that swims upright like a standard fish to an adult that lies on one side, with both eyes on the upper side, having rotated posture 90 ° relative to gravity and the former normal posture. Adult Citharichthys stigmaeus and Hypsopsetta guttulata were used in behavioural and physiological experiments to determine whether the postural change is a peripheral or central phenomenon. Cleared and sectioned specimens verify that the otolith organs, unlike the eyes, do not rotate within the skull, and so do not maintain the normal vertebrate orientation with respect to gravity. Ocular compensation to lateral tilt shows that tactile cues, vision, and the semicircular canals are inadequate to produce tilt responses, but elimination of otolith function abolishes tilt responses. The major postural role of the otolith organs is not lost. Selective removal of otoliths demonstrates that the flatfish utriculus has only a minor role in tilt responses, and that the sacculus-lagena is required, unlike the situation in other vertebrates. The details of the ocular compensation responses are similar to those of standard fishes. Each sacculus lies at an angle of up to 45 ° when in the normal position, but unilateral loss does not change the phase of the response curve, indicating that the null response is set for a non-zero value of gravitational shear, unlike the null at zero shear to the utriculus in other vertebrates. Hysteresis effects suggest a differential sensitivity between tilts near the normal and the upside-down null positions. The narrowness of the effect argues against mechanical restrictions. Possibly the vertical utriculus is useful only near the normal, as an accessory organ, like the vertical lagena in other vertebrates. Neural units recorded from both eighth nerve and medulla show the expected activity properties of regular and irregular rate, tonic and phasic responses to tilt, directional dependence and ‘multi-valuedness’, as in other vertebrates. No novel response types are found, nor any distinctive ‘into-level’ types described for some vertebrates. Vibration sensitivity is associated with irregular rate, and exclusively vibration-sensitive units are apparent only in the utriculus. The shift in functional relations of the otolith organs relative to gravity is not apparently compensated for by any major change in peripheral afferent gravistatic unit properties. An increasing distinction between the null at normal and the null upside-down is shown by limited data on ocular compensation in three year-classes of flatfish. A central change in vestibular function is suggested that might be dependent on experience, as is gradual compensation to a vestibular lesion. Since peripheral changes are not responsible for the postural change, alternative central mechanisms are proposed, including central weighting of input, recognition of a complex input pattern, and plasticity of connexions, all of which have received some supporting evidence from these results.
Effects of Partial Caudal-Fin Amputation on the Kinematics and Metabolic Rate of Underyearling Sockeye Salmon (Oncorhynchus Nerka) At Steady Swimming Speeds
Authors: Webb P. W.
Published: April 2021

Propulsive wavelength, tail-beat frequency, trailing-edge amplitude, critical swimming speed and oxygen consumption rates have been measured for sockeye salmon in which the trailing edge depth and caudal-fin area were variously reduced by partial caudal-fin amputation. The swimming mode was sub-carangiform. The 45 min critical swimming speed for intact fish was 61·6 cm/sec (3·0 l/sec). The critical speed was not significantly reduced by removal of either the epaxial or hypaxial caudal-fin lobes, but was reduced significantly (P < 0·05) to 51·8 cm/sec (2·5 l/sec) when both lobes were removed. The mean length of the propulsive wave was 1·00 body length, and was not affected by the caudal-fin surgery. Both tail-beat frequency and amplitude increased with speed, their product linearly so. Normalization of data in relation to the physiological maximum at the critical swimming speed showed no relative changes in frequency and amplitude. No significant differences were observed in standard or active metabolic rates. General equations describing thrust (Lighthill, 1969) and drag were compared. It was shown that the drag on the caudal fin was markedly increased by lateral propulsive movements as suggested by Bone ‘s boundary-layer thinning hypothesis (Lighthill, 1971). Drag coefficients for the caudal fin were one to two orders of magnitude higher than would be expected in the absence of lateral movements. It is considered that the principal function of the caudal fin is in manoeuvre and acceleration.
The Relations Between Membrane Potential and Parameters of Ciliary Beat in Free-Swimming Paramecium Caudatum
Authors: Offen R. J. , Roberts A. M.
Published: April 2021

A method of analysing the parameters of ciliary beat as a function of membrane potential in free-swimming organisms is presented. The method obviates artefacts which may be produced on impaling small organisms with micro-electrodes. Changes in the membrane potential of Paramecium caudatum produce two effects : an increase in frequency of beat of up to (23 ± 3) % mV−1 at 25 °C for both depolarizations and hyperpolarizations which falls to zero within a few minutes, and a change in the direction of ciliary beat of (9 ± 1) degree mV-1 for depolarizations only, which in a spiralling organism do not accommodate to the field. The orientation of P. caudatum towards the cathode in an electric field is due principally to changes in the angle of ciliary beat on the cathodal side of the organism ; changes in frequency seem to be relatively unimportant. Axial spinning during normal locomotion in P. caudatum is satisfactorily accounted for by transverse components of ciliary thrust. The oblique orientation of P. caudatum near boundaries is caused by an asymmetry (geometrical or electrical or both) over the surface of the organism. Comparison with observations on extracted organisms indicates that a change in the direction of beat of 9° is associated with an increase in calcium concentration at the ciliary apparatus of about 25 %.
Motor Activity During Walking in the Cockroach Periplaneta Americana
Authors: Delcomyn Fred
Published: April 2021

The patterns of electrical activity in selected muscles of the rear legs were studied during locomotion in tethered cockroaches. Stepping movements did not appear significantly different in a tethered insect compared to one which was freely moving. During walking, the muscle potentials due to ‘fast’ flexor and ‘slow’ extensor motoneurones were always grouped into alternating bursts separated by periods of silence, but those due to ‘slow’ flexor motoneurones were not usually grouped in this way. Muscle potentials due to ‘slow’ flexor activity were usually modulated in frequency such that the highest frequencies occurred when in the free-walking insect one would have expected a burst to occur. ‘Slow’ extensor and ‘fast’ flexor bursts were studied in detail. Minor fluctuations of the frequency of impulses within each burst were not related to any other parameter of activity which was measured. For ‘slow’ extensor bursts, the duration of the bursts, the number of impulses per burst and the mean interval between impulses in a burst each increased significantly as the duration of the associated step increased. As in free-walking animals, the rate at which the latter two changed as a function of step duration was often significantly higher for steps shorter than about 300 msec, than for longer ones. However, the absolute value of these two parameters in tethered preparations was about half that at corresponding step durations in free-walking preparations. For ‘fast’ flexor bursts, weak positive correlations between step duration and burst duration, number of impulses per burst and mean interval per burst could be demonstrated only in a few preparations. The relationships were not significantly different from those seen in free-walking preparations. The results suggest that reflex feedback loops can strongly affect some parameters of motor output, such as discharge rate within a burst, but affect others, such as burst duration, only very slightly if at all. A model of the mechanism by which steps may be generated is modified accordingly.
Contraction Kinetics of the Fast Muscles Used in Singing by A Katydid
Authors: Josephson R. K.
Published: April 2021

The sound-pulse frequency, and by inference the wing-stroke frequency, in the song of the katydid, Euconocephalus nasutus, is 160 Hz. The thoracic temperature during singing is 36 °C, which represents a gradient between the insect ‘s thorax and its environment of 12 °C. Contraction kinetics were measured as a function of temperature for a singing muscle (first tergocoxal forewing muscle of males) and homologous, purely flight muscles (forewing muscles of females, hindwing muscles of males). Because the performance of the singing muscle was found to be easily degraded, the measurements were made from nearly intact animals. At 35 °C the contraction rise time for an isometric twitch of a singing muscle is 7·7 msec. The twitch duration, measured from onset to 90% relaxation, is 12·2 msec. Purely flight muscles are about half as fast, but develop more tension per crosssectional area, both in twitches and tetani. The temporal characteristics of twitch contractions, including the delay between the onset of the muscle action potential and the onset of contraction, have Q10 values between 1·5 and 2. At 35 °C a singing muscle contracts in an unfused tetanus when stimulated at 150 Hz, relaxing about half-way between tension peaks. This result suggests that this is the way the muscle operates during singing. At 25 °C the muscle contracts in a smooth tetanus when stimulated at 150 Hz. A warm thorax is not only a consequence of the intense activity during singing but also necessary for the performance achieved. Isometric twitch tension is maximum at muscle lengths more than one-third greater than the in situ length. Twitch contraction time is nearly independent of muscle length but relaxation time increases as the muscle is stretched.
A Technique for the Cultivation of Insect Tissues
Authors: Frew J. G. H.
Published: April 2021

In vitro tissue culture is shown to be a possible mode of experimentation with the tissues of the Blow Fly larva. Methods are described-whereby the tissues, and the body fluids requisite as culture media may be obtained free from bacteria. The imperfections of the technique are noted and the conclusion reached that a successful technique must depend on the rearing of bacteria-free larvae, for which a method is briefly outlined. It is shown that progress in this part of the work must await further physiological knowledge, particularly in respect to the nature of the body fluids.
Observations on the Physiology of the Swim Bladder in Cyprinoid Fishes
Authors: Evans H. M. , Damant G. C. C.
Published: April 2021

The swim bladder of fishes is primarily a hydrostatic organ and with rare exceptions contains or tends to contain the exact quantity of gas which is necessary to make the specific gravity of the whole fish equal to that of the water in which it is swimming, so that it can rest in mid-water tending neither to rise nor sink: this normal condition is called neutral buoyancy. Since gas is compressible and water is not, any increase of external or atmospheric pressure by acting through the non-rigid body walls will reduce the volume of gas in the swim bladder and cause the fish to sink in the water (condition of negative buoyancy). This condition can also be produced by aspirating some of the gas from the swim bladder or by attaching a small weight to the fish.
A New Type of Mammalian Intersexuality
Authors: Baker John R.
Published: April 2021

(1) In certain islands of the New Hebrides (in the Pacific Ocean) a considerable proportion of the pigs are intersexual. Nowhere in the world are intersexual mammals so abundant. (2) These intersexes differ from the rare intersexes of European pigs in the invariable absence of any rudiment of uterus or vagina. (3) A tendency to intersexuality is inherited. (4) The intersexes are interpreted as genetic males in which the testicular hormone has been produced too late in development.
The Effect of Variation in Relative Humidity on Certain Species of Collembola
Authors: Davies W. Maldwyn
Published: April 2021

Authorities have differed regarding the optimum degree of moisture associated with the presence of Collembola. Experiments have, therefore, been carried out to ascertain the influence of variation in relative humidity on the death-rate of certain species of these insects. At a uniform temperature of 25° C. it was found that saturated conditions of the environment are necessary for the survival of all species of Collembola used in the experiments. It has been found that, with the exception of the genus Entomobrya, Collembola devoid of a tracheal system are very susceptible to dry conditions. Sminthurus viridis, which possesses a tracheal system and well-developed ventral tube, is much less susceptible to atmospheric dryness. An experiment carried out with Sminthurus viridis suggests that the ventral tube is used for conveying droplets of water from the hairs of the body to the mouth. It also serves as a “cleaning” organ. The results of the above experiments have had direct practical application in methods of control of Collembola.
The Relation of Electrolytes to the Cardiac Rhythm of Palinurus (Jasus) Lalandii and Octopus Horridus
Authors: Zoond Alexander , Slome David
Published: April 2021

The heart of Palinurus lalandii and the ventricle of Octopus horridus maintain their normal rhythm for long periods in solutions containing only sodium and calcium chlorides. The removal of calcium from the perfusion fluids causes systolic arrest in both hearts. Both hearts are sensitive to very low concentration of potassium when perfused with potassium-free fluid. Excess of magnesium and strontium produce the same effect as excess of calcium, but magnesium cannot be successfully substituted for calcium in the perfusing fluid. The physiological range of H ion concentration is determined for the two preparations. Both hearts have low temperature optima, and the high limit of their range is in the neighbourhood of 20° C.
The Growth of Fish
Authors: Gray J.
Published: April 2021

For the egg of any given species of animal there exists a range of temperature within which the embryo is capable of developing into a normal healthy organism. If the temperature of incubation be raised, the velocity of development of a cold-blooded embryo is increased ; if the temperature be lowered the velocity is decreased. In both cases the result is qualitatively similar; the mutual proportions of the various tissues and organs are, as far as is known, much the same in the final products. It is improbable that the velocity of every process which occurs during development is equally affected by changes in temperature; some processes will tend to respond to a greater extent than others. If, therefore, development were simply the summation of each separate process we would expect to find that the relative size of each organ would vary with the temperature at which the egg had been incubated. Consider, for example, two cells each capable of reproducing itself in 12 hours at 10° C. but differing from each other in their temperature coefficients of growth. If a rise of 10° C. increased the rate of development of one cell by 100 per cent., and that of the other by 200 per cent., then at the end of 12 hours’ development at 20° C. there would be five cells of one type for every seven of the other, whereas at 10° C. the numbers would be equal. The very fact that marked variations in the proportionate size of organs and tissues do not apparently characterise variations in the temperature of incubation indicates that, to some extent, the velocity of development of any one type of tissue or the velocity of any one embryological process is dependent on the velocity of other parallel processes, or that they are all controlled by the velocity of one fundamental reaction. By varying the temperature of incubation of the eggs of the trout, a convenient means exists of determining how far this picture of the embryological development of a fish is true, or how far some processes can be regarded as independent reactions.
On the Nature of Hereditary Size Limitation
Authors: Robb Robert Cumming
Published: April 2021

During recent years several attempts have been made to examine the processes of organic growth from the standpoint given by a chemical reaction of an autocatalytic nature. It is the purpose of this communication to extend the examination of this concept of metazoan size limitation in the light of new data on the growth of giant and pigmy rabbits.
On the Nature of Hereditary Size Limitation
Authors: Robb R. Cumming
Published: April 2021

If it could be shown that the determination of organ size in the animal body is not reached by an independent process, but that the magnitude of any one structure is determined by that of others, such evidence, if of a strictly quantitative nature, would tend to affirm the existence of a physical mechanism regulating the relative growth of body components. It is the object of this paper to present such evidence, and to describe a model from physical chemistry which lends a reasonable interpretation to the diversification observed in the ontogenetic and phylogenetic history of organ size.
The Effect of Extracts of Suprarenal Cortex on the Blood Calcium
Authors: Mirvish L. , Bosman L. P.
Published: April 2021

An extract has been prepared from the suprarenal cortex, which, when injected into rabbits, lowers the blood calcium to the extent of about 30 per cent. ; the maximum fall occurs after 24 hours, and returns to normal in about 48 hours. The extract prepared from the suprarenal cortex resembles that obtained from ovary and corpus luteum, both in physical characteristics, and in the production of a typical response on the part of the blood calcium. It would appear that the hormone of the suprarenal cortex that is capable of lowering the blood calcium is very similar and possibly identical with the hormone of the ovary, having the same function. A definite relationship has been established between the suprarenal cortex and the ovary, justifying the long-suspected connection between the two glands.