bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Pacemaker Systems in the Hydroid Tubularia
Authors: Josephson R. K. , Uhrich J.
Published: April 2021

Of the three conducting systems known in the stalk of Tubularia—the slow system (SS), the triggering system (TS), and the distal opener system (DOS)—the SS can be eliminated as being necessarily involved in the pacemaker system inhibition seen during continued stalk stimulation because its threshold is higher than the minimal stimulus strength required for inhibition. The TS can also be eliminated as the inhibitory pathway because (1) separating a polyp from a colony and hence from a source of continued input along the TS does not result in an increase in the spontaneous activity of the polyp above that of appropriate controls, and (2) distal tentacle stimulation which activates the DOS but not the TS is more inhibitory than is stalk stimulation which excites both the TS and the DOS. The inhibitory pathway is apparently the DOS or, less likely, a yet unidentified conducting system in the stalk. Inhibitory stimulation suppresses both single pulses and bursts in the NP pacemaker system and it is likely that the HP pacemaker system is also inhibited. The greater the background level of spontaneous activity the greater is the effectiveness of inhibitory stimulation. The period of inhibition lasts for a few seconds after each stimulus.
Aspects of the Physiology of Terrestrial Life in Amphibious Fishes
Authors: Gordon Malcolm S. , Boetius Inge , Evans David H. , McCarthy Rosemary , Oglesby Larry C.
Published: April 2021

Bony fishes which could spend periods of time out of water, but which lacked special anatomical modifications for survival out of water, were probably involved in the early stages of the evolution of terrestrial life in the vertebrates. The rhipidistian crossopterygians were apparently the group ancestral to all higher vertebrates (Romer, 1966; Schmalhausen, 1968), but they are unavailable for study of possible physiological adaptations to life on the land. One way we may obtain some idea of the possible range of physiological adaptations which might have been possessed by these ancestral forms is to make comparative studies of pertinent aspects of the physiology of living amphibious fishes. We define amphibious fishes as those which spend periods of time out of water, on or above the ground surface, as normal parts of their life-histories. The most relevant forms are those lacking specialized accessory respiratory organs.
Urine Formation by the Malpighian Tubules of Calliphora
Authors: Berridge M. J.
Published: April 2021

The ability of chloride and phosphate to support urine formation has been studied under different conditions. When sulphate is used as a balancing anion, rate of urine formation is linearly related to the external chloride or phosphate concentration. Tubules can concentrate phosphate in the urine by a mechanism which is independent of other anions. Phosphate U/P declines with an increase in external phosphate concentration. In the absence of phosphate, chloride is slightly concentrated in the urine. Chloride U/P is reduced by phosphate but unaffected by sulphate. When an extensive series of anions was tested, rate of urine production was related to the size of the anions. Phosphate was the only exception because despite its large size it supported the highest rate of urine production. Arsenate competitively inhibits phosphate transport, resulting in an augmentation of chloride transport. Copper, however, blocks urine formation in the presence of chloride but not in the presence of phosphate. The experiments indicate two separate mechanisms for anion transport. Anions such as chloride probably pass through pores with an estimated radius of 3·6 Å., whereas phosphate is transported by a carrier.
The Physiology of the Antennal Gland of Carcinus Maenas (L.) III. Glucose Reabsorption
Authors: Binns R.
Published: April 2021

Glucose is actively reabsorbed by the antennal gland. In 100% sea water there is a blood threshold concentration of approximately 150 mg.%. This does not indicate the maximum rate of glucose reabsorption. Below the threshold, reabsorption is not always complete, but may be if carbohydrate sources are limited or absent. The threshold level depends on the rate at which fluid passes through the antennal gland, an increase in urine production rate being correlated with a reduction in the glucose threshold. Phloridzin inhibits reabsorption and glucose U/B ratios approach unity, indicating that glucose is filtered passively into the antennal gland.
Visual Thresholds and Spectral Sensitivity of Flatfish Larvae
Authors: Blaxter J. H. S.
Published: April 2021

Plaice and sole larvae have a pure-cone retina and no retinomotor responses. Observations on the extinction of phototactic and light-dependent feeding behaviour, using both white and coloured light, enabled visual thresholds and spectral sensitivity to be determined. Visual threshold decreased (that is, sensitivity increased) with age. The values for extinction of negative phototaxis ranged from 10−4−10−6 m.c. Sole larvae could feed in the dark from the early post-hatching stage, plaice larvae only at metamorphosis. Thus light intensity thresholds for feeding were only determinable in younger plaice larvae. The values ranged from 10°−10−2 m.c. The spectral sensitivity curves were plateau-like and photopic in nature. Thus the larval cones have spectral properties similar to those of adult teleosts. The differences in threshold obtained by the two techniques are probably a measure of the extent of recruitment of high-threshold cones required for image formation in feeding. No evidence of a dermal light sense was found.
The Circadian Rhythm of Flight Activity in the Mosquito Aedes Aegypti (L.): The Phase-Setting Effects of Light-on and Light-Off
Authors: Taylor B. , Jones M. D. R.
Published: April 2021

The circadian flight-activity of individual, sugar-fed Aedes aegypti females has been studied, using the flight-sound as an indicator of activity. The activity appears to be controlled by an endogenous rhythm with a period of 22–24 hr-in constant dark and about 26 hr. in constant light. Both light-on and light-off have phase-setting effects. Under favourable conditions, peaks of activity occur 13–14 hr. after light-on and 22–23 hr. after light-off. Both these peaks persist in constant dark following an LD 4:20 regime. The total amount of flight-activity is correlated with the duration of light (70 lux) in the 24 hr. period.
A Study of the Instantaneous Air Velocities in a Plane behind the Wings of Certain Diptera Flying in a Wind Tunnel
Authors: Wood James
Published: April 2021

The variations in several kinematic parameters of Calliphora erythrocephala were studied on flies flying in a wind tunnel. Variation was equally pronounced at both the and bottom of the wingstroke. The wakes of Calliphora erythrocephala and Phormia regina flying in moving air exhibited extremely low turbulence, while considerable turbulence indicative of stall was present in the wakes of flies flying in still air. The air velocities recorded as functions of time in the wakes of both Phormia and Calliphora are consistent with most lift being produced in the downstroke, with the first part of the upstroke also contributing to the production of lift.
Characteristics of Transmission Failure in the Squid Stellate Ganglion: A Study of A Simple Habituating System
Authors: Horn G. , Wright M. J.
Published: April 2021

When certain vertebrate and invertebrate interneurones are repeatedly stimulated through the sense organs, or by electric shocks delivered to sensory nerves, their response gradually fails. Typically the stimulus is delivered once every few seconds and the response consists of action potentials (e.g. Bell, Buendia, Sierra & Segundo, 1964; Horn & Hill, 1964, 1966; Horridge, Scholes, Shaw & Tunstall, 1965; Horn & Rowell, 1968) or excitatory postsynaptic potentials (Bruner & Tauc, 1966; Spencer, Thompson & Neilson, 1966; Segundo, Takenaka & Encabo, 1967 a). The physiological basis of this response decrement is not known though synaptic depression, desensitization of the postsynaptic membrane, accumulation of potassium ions in the extracellular clefts and build up of pre-and postsynaptic inhibition have all at one time or another been invoked.
Mechanisms for the Control of Body Temperature in the Moth, Hyalophora Cecropia
Authors: Hanegan James L. , Heath James E.
Published: April 2021

Thoracic temperature in the moth, Hyalophora cecropia, is correlated with gross patterns of behaviour. The animal warms up to a minimum of 34·8 °C body temperature before initiating flight. The rate of warm-up is linear and the duration of the warm-up period increases with decreasing air temperature. Thoracic temperature at the initiation of flight and during maintained flight remain constant at any given air temperature, however, decreases 0·25 °C per °C gradient as air temperature is decreased. Distribution of the maximum and minimum thoracic temperatures during active periods indicate that the animal maintains its body temperature within a favourable range. The animal uses behavioural mechanisms to maintain the thoracic temperature within this range when the body temperature reaches the limits, 33·4 and 37·8 °C. The minimum thoracic temperature for flight (34·8 °C) and the shade-seeking temperature (38·5 °C) correspond closely to the limits predicted from the maximumminimum distribution of thoracic temperatures. The theoretical minimum and maximum rates of oxygen consumption were calculated from cooling curves and warm-up curves. Both rates increase when the gradient between body temperature and air temperature increases (air temperature is lowered, body temperature remains relatively constant). Directly measured rates of oxygen consumption in flying animals increase as air temperature decreases. These values fall within the calculated maximum and minimum in all cases. Oxygen consumption measured in torpid animals indicates a normal poikilo-thermic response, increasing with increased air temperature. The Q10 for this response is 2·25 over the range 20–30 °C. A model for the regulation of body temperature in active moths is discussed.
Detour Experiments with Split-Brain Octopuses
Authors: Wells M. J.
Published: April 2021

Octopuses will move out of sight of their prey and make detours through a maze to get crabs that are initially visible but not directly accessible to them. Successful detours are made without training, and performance shows little change with practice. Longitudinal division of the vertical and subvertical lobes and/or of the superior and inferior frontal lobes does not affect performance. Extension of the cut downwards to include the optic commissures produces animals that sometimes perform quite normally, and at other times vacillate, apparently unable to prevent the onset of incompatible responses arising from visual inputs to the two sides of the body. If the optic nerves are cut on once side such animals perform normally. In the intact octopus conflict between the two sides must be avoided by exchange of information through the optic commissures, or though structures closely associated with these. This situation is compared with that found in training experiments involving visual discrimination. In detours the information acquired through one eye modifies the behaviour of both sides of the body for a few minutes. Its availability is not changed by prior removal of the superior frontal and/or vertical lobes. Following unilateral training involving visual discrimination, responses arising as a result of visual inputs to either side of the body are modified for many weeks, but only provided that the superior frontal-vertical lobe system remains intact. If this system is split the untrained side remains naive. It is concluded that the long and short-term storage of representations of objects seen must be different in kind and that the establishment of long-lasting bilateral traces involves structures that are not essential for the side-to-side distribution of information in the short-term situation. This state of affairs is compared with the situation in touch learning, where there seems to be no functional equivalent of the optic commissures. Long-term bilateral traces are established as a result of unilateral training but the effect takes an hour or more to spread to the untrained side.
The Influence of the Diuretic Hormone On the Process of Urine Secretion by the Malpighian Tubules of Carausius Morosus
Authors: Pilcher Diana E. M.
Published: April 2021

The rate of urine secretion and the trans-wall potential have been measured in single, isolated Malpighian tubules in media of varying ionic composition. Potassium, present as the only monovalent cation in a saline, is able to support urine secretion at a higher rate than sodium. In the absence of sodium, the rate of urine secretion depends upon the concentration of potassium, but is enhanced in the presence of sodium, especially at low potassium concentrations. The replacement of part or all of the anions normally present in saline by sulphate results in a reduction in rate of urine secretion and a rise in trans-wall potential. Neither the rate of urine secretion nor the trans-wall potential is affected by ouabain, but both are reduced by 2,4-dinitrophenol. The ionic composition of the urine remains unchanged by the addition of diuretic hormone to the medium surrounding the tubule, but the rate of urine secretion and the trans-wall potential are increased. It is suggested that the diuretic hormone acts by stimulating active potassium transport.
Conduction Along the Ventral Nerve Cord of A Hemichordate Worm
Authors: Pickens Peter E.
Published: April 2021

Compound and all-or-none pulses have been recorded from the ventral nerve cord of a hemichordate worm. Compound pulses are composed of at least four smaller pulses, suggesting that four conduction pathways may be present in the cord. Conduction velocities in the anterior ventral cord are as high as 1.1 m/s but fall to about half this value in the posterior cord. In both parts of the cord the passage of the first pulse facilitates the passage of the second so that conduction velocities are increased by 10 to 20%. Paired or multiple stimuli produce repetitive firing and facilitation of size and number of pulses in the cord. Although strong or repeated shocks evoke local, graded muscle potentials, no correlation has been found between the size of these potentials and the number of pulses in the cord. Integration occurs in the hepatic region of the cord. It is the most labile to through-conduction, output from this region does not have a one-to-one relation to input, and pulses originating in the posterior cord and travelling toward the collar are usually blocked in this area.
A Gas-Chromatographic Micromethod for Respiration Studies On Insects
Authors: Tadmor U. , Applebaum S. W. , Kafir R.
Published: April 2021

A gas-chromatographic method adapted for measuring both oxygen consumption and carbon dioxide release of individual insects is described. The method is based on initial separation of air from CO2 on Porapak Q, and subsequent separation of oxygen from nitrogen on molecular sieve 5 A. 1−2 μl. of O2 or CO2 are easily measured with the thermal conductivity apparatus used. Representative respiratory values of field-collected and laboratory-reared adult Chilocorus bipustulatus beetles are presented in order to show the capability of the method.
Recovery Course of Excitability in A Single Neurone of Onchidium Verruculatum
Authors: Katayama Yoshifumi
Published: April 2021

The electrical excitability of a nerve cell of Onchidium verruculatum was measured by transmembrane depolarizing current pulses through a glass-capillary microelectrode inserted into the soma of the nerve cell.

The strength-duration and the strength-latency relations were measured during the resting state of a silent-type nerve cell, and both were represented by hyperbolic curves. This shows that the minimum quantity of electricity (that is, current strength multiplied by time duration required to produce a spike) must pass through the membrane to discharge impulses in the resting state of the nerve cell. The strength-latency relations were obtained after a spontaneous spike. The stimulus began during the falling phase of a preceding firing and lasted for 300 ms. These relations were represented by two exponential terms. The strength-duration relations were measured at various times after a preceding discharge and these were also represented approximately by hyperbolic curves in regularly firing or frequently firing neurones. These results suggested that a minimum quantity of electricity must be required to elicit a second spike at a given time interval after a preceding spike; and that the reciprocal of this value might represent the excitability after that time interval. The time course of the reciprocal of the quantity referred to above expresses the process of the recovery of excitability in the nerve cell after a spike. This process can be expressed mathematically by two exponential terms.
Unidirectional Rotation Neurones in the Optomotor System of the Crab, Carcinus
Authors: Wiersma C. A. G. , Fiore L.
Published: April 2021

Among the optomotor fibres to the eye muscles in Carcinus a class was found which responds to unidiiectional fast rotations around various body axes. All had large signals and are therefore of large diameter. In one set of these fibres which fires especially for rotations around the dorsoventral axis, it could be shown that discharges take place especially during accelerations and that, when a rotation in the null direction is suddenly stopped, a short discharge occurs. The fibres for other axes behave in a similar manner. For rotations around the ventro-dorsal axis, but not for other directions, mediumsized fibres are present which, in contrast to the fast fibres, respond to visual stimulation, as well as to body rotations in darkness, thus combining the input properties of the unidirectional fast rotatory and the unidirectional purely optokinetic small fibres. Their sensitivity to visual input is for low rotation velocities, to body lotations is for high rotation velocities.
Coxal Muscle Receptors in the Crab: The Receptor Current and Some Properties of the Receptor Nerve Fibres
Authors: Roberts Alan , Bush B. M. H.
Published: April 2021

The resting membrane potential of S and T receptor fibres is usually –50 to – 60 mV and is potassium dependent. The neurone membrane may also be permeable to other ions or some part of it may be inaccessible. The electrical responses of the fibres are nearly ohmic for 40 mV on either side of the resting membrane potential. In some fibres there is a little depolarizing electrogenesis. Receptor potentials were evoked by ‘step’ pulls on the receptor muscle. In response to fast pulls there is often a variable spike component, abolished by tetrodotoxin and presumably therefore sodium dependent. Ion substitution experiments indicate that the rest of the receptor potential is also mainly sodium dependent. However, in the absence of sodium a small receptor response remains. Possible reasons for this are discussed.
Mechanical Properties of the Longitudinal and Circular Muscle in the Earthworm
Authors: Tashiro N.
Published: April 2021

The mechanical properties of the longitudinal and circular muscles of the earthworm, Pheretima communissima, were studied in various solutions. In the longitudinal muscle, field stimulation elicited two distinct waves of tension development, i.e. phasic and tonic contractions. But in the circular muscle, these components were not distinguishable. The phasic contraction in the longitudinal muscle increased in sodium-free (tris) solution while the tonic contraction was abolished. Neither the phasic nor the tonic contraction, however, was influenced by tetrodotoxin (3×10−8 M), d-tubocurarine (1·4 × 10−s M), or atropine (3·5 × 10−5 M). The contraction in the circular muscle was suppressed in sodium-free solution and also by tetrodotoxin (3×10−8 M), but was not affected by d-tubocurarine (1·4 × 10−;5 M) or by atropine (3·5 × 10−8 M). It is speculated that the phasic contraction of the longitudinal muscle is triggered by a calcium spike, and the contraction in the circular muscle is preceded by a sodium spike in muscle fibres.
Gliding Flight of the White-Backed Vulture Gyps Africanus
Authors: Pennycuick C. J.
Published: April 2021

Glide-comparison measurements were made on ten species of East African soaring birds using a Schleicher ASK-14 powered sailplane. Horizontal and vertical speed differences between bird and glider were measured by a photographic method, and used to estimate the bird’s horizontal and vertical speeds relative to the air. The analysis refers to the white-backed vulture, since by far the largest number of measurements was obtained on this species. A regression analysis using a two-term approximation to the glide polar yielded an implausibly high estimate of induced drag, which was attributed to a lack of observations at lift coefficients above 0 72. An amended glide polar was constructed assuming elliptical lift distribution and a maximum lift coefficient of 1-6 to define the low-speed end, while the high-speed end was made to pass through the mean horizontal and sinking speeds of all the experimental points. This curve gave a minimum sinking speed of 0·76 m/s at a forward speed of 10 m/s, and a best glide ratio of 15·3:1 at 13 m/s. It did not differ significantly (in the statistical sense) from the original regression curve. In comparing the estimated circling performance, based on the amended glide polar, with that of the ASK-14, it was concluded that the rates of sink of both should be comparable, but that the glider would require thermals with radii about 4-3 times as great as those needed to sustain the birds. The conclusions are consistent with experience of soaring in company with birds. In an attempt to assess the adaptive significance of the low-aspect-ratio wings of birds specializing in thermal soaring, the white-backed vulture’s circling performance was compared with that of an ‘albatross-shaped vulture’, an imaginary creature having the same mass as a white-backed vulture, combined with the body proportions of a wandering albatross. It appears that the real white-back would be at an advantage when trying to remain airborne in thermals with radii between 14 and 17 m, but that the albatross-shaped vulture would climb faster in all wider thermals ; on account of its much better maximum glide ratio, it should also achieve higher cross-country speeds. It is concluded that the wing shape seen in vultures and storks is not an adaptation to thermal soaring as such, but is more probably a compromise dictated by take-off and landing requirements. The doubts recently expressed by Tucker & Parrott (1970) about the results and conclusions of Raspet (1950a, b; 1960) are re-inforced by the present experience.
The Respiratory System of the Egg-Shell of Homorocoryphus Nitidulus Vicinus (Orthoptera, Tettigoniidae)
Authors: Hartley J. C.
Published: April 2021

An account is given of the structure of the egg-shell of Homorocoryphus nitididus vicinus based on conventional and scanning electron microscopy. The respiratory rates of the egg in air and under various degrees of flooding have been measured. The problems of oxygen diffusion through egg-shells of this type have been subject to mathematical analysis. The hypothetical and observed results for oxygen diffusion compare favourably, confirming that the respiratory system functions as suggested. The eggs of Homorocoryphus cannot be said to have a plastron, and it is suggested that water retention may be more important than a high respiratory efficiency under water. A distinction is drawn between respiratory efficiency of an egg under water and plastron efficiency.
Control of Gliding Angle in Rüppell’s Griffon Vulture Gyps Rüppellii
Authors: Pennycuick C. J.
Published: April 2021

The drag of the frozen, wingless body of a Rüppell’s griffon vulture was measured in a wind tunnel with a simple drag balance. The drag coefficient with feet and neck retracted was 0·43, based on the greatest cross-sectional area of the body. The drag of the body was trebled by fully lowering the feet, and more than quadrupled when the tail was lowered as well, apparently owing to separation of the flow over the back. The drag coefficient of the legs and feet, based on their frontal area, varied from 0·89 to 1·08 in different positions. At low speeds the use of the feet alone should reduce the glide ratio from about 15 to 10, but the airbrake effect becomes progressively more marked at higher speeds. At lower speeds reduction of the wing area produces a greater steepening of the gliding angle, but at the expense of increasing the minimum speed. Increase of induced drag would provide a highly effective gliding angle control at very low speeds, and it is suggested that this is achieved by raising the secondary feathers, which would alter the spanwise lift distribution by transferring a greater proportion of the lift to the primaries.
Respiratory Exchange and Body Size in the Aldabra Giant Tortoise
Authors: Hughes G. M. , Gaymer R. , Moore Margaret , Woakes A. J.
Published: April 2021

The O2 consumption and CO2 release of nine giant tortoises Testudo gigantea (weight range 118 g–35·5 kg) were measured at a temperature of about 25·5 °C. Four European tortoises Testudo hermanni (weight range 640 g-2·16 kg) were also used. The mean RQ values obtained were 1·01 for T. gigantea and 0·97 for T. hermanni. These values were not influenced by activity or size. The data was analysed by plotting log/log regression lines relating body weight to O2 consumption. Both maximum and minimum metabolic rates recorded for each individual T. gigantea showed a negative correlation with body weight. For active rates the relation was O2 consumption = 140·8 W0·97, whereas for inactive animals O2 consumption = 45·47 W0·82. The maximum rates were obtained from animals that were observed to be active in the respirometer and the minimum rates from animals that remained quiet throughout. The scope for activity increased with body size, being 82 ml/kg/h for animals of 100 g and 103 ml/kg/h for 100 kg animals. The corresponding ratio between maximum and minimum rates increases from about 2 to 6 for the same weight range. Values for metabolic rate in T. hermanni seem to be rather lower than in T. gigantea. Analysis of the relative proportion of the shell and other organs indicates that the shell forms about 31 % of the body weight in adult T. hermanni but only about 18% in T. gigantea of similar size. The shell is not appreciably heavier in adult T. gigantea (about 20 %). Data obtained for inactive animals is in good agreement with results of other workers using lizards and snakes. Previous evidence suggesting that chelonians show no reduction in metabolic rate with increasing size is not considered to conflict with data obtained in the present work.
Respiratory and Circulatory Responses of Rainbow Trout Larvae to Carbon Monoxide and to Hypoxia
Authors: Holeton G. F.
Published: April 2021

Larval trout undergo a transition from cutaneous respiration to gill respiration which at 10 °C is well advanced by the 18th day after hatching. Resting heart rate of newly hatched trout increases during the first few days, stabilizes for a while, and then drops between the 9th and 18th day after hatching. This drop may be the result of establishment of ‘vagal tone’. The basic breathing response of larval trout when hypoxic is an increase in fin movements and an increase in rate and amplitude of breathing, but breathing movements slow and weaken if environmental falls much below 40 mmHg. With trout up to 8 days after hatching hypoxia causes a tachycardia. At very low levels there is a drop in heart rate and in the amount of blood pumped by the heart. Upon restoring oxygen to very hypoxic larvae, the heart rate recovers slowly, unlike the quick abolition of bradycardia of adult fish. It appears that up to the age of 8 days from hatching, trout do not have a functional bradycardia reflex associated with hypoxia. The responses of larval trout to CO and to hypoxia, and of adult trout to CO, are similar in nature. It is proposed that the basic response to anoxaemia is an increase in breathing and circulation and that the adult bradycardia response to hypoxia is a superimposed mechanism which relates circulation to the quantity of oxygen presented to the gills.
Gliding Flight of the Dog-Faced Bat Rousettus Aegyptiacus Observed in a Wind Tunnel
Authors: Pennycuick C. J.
Published: April 2021

A bat was trained to fly in a tilting wind tunnel. Stereoscopic photographs were taken, both by reflected and by transmitted light, and measurements of best gliding angle were made. Variation of wing span and area at different speeds was much less than in birds. This is attributed to the construction of the wing, which prevents the bat from folding back the manus in flight, because this would lead to collapse of the plagiopatagium. The trailing edge of the wing is normally deflected upwards in flight, at least in the distal parts. This is interpreted as providing longitudinal stability. The plagiopatagialis proprii muscles appear to act as an elevator, by deflecting the trailing edge of the plagiopatagium upwards. The speed range over which the bat could glide was 5·3–11·0 m/s. Its maximum lift coefficient was 1-5, and its best glide ratio 6·8:1. The Reynolds number range, based on mean chord, was 3·26 × 104 to 6·79 × 104. A simple regression analysis of the glide polar indicated a very high span efficiency factor (k) and low wing profile drag coefficient (Cdp). On the other hand, a drag analysis on the assumption that k = 1 leads to an improbably large increase in the estimated Cdpat low speeds. It is suggested that the correct interpretation probably lies between these extremes, with k ≈ 1·5; Cdp would then be about 0·02 at high speeds, rising to somewhat over o-i at the minimum speed. It would appear that the bat is not so good as a pigeon at fast gliding, but better at low-speed manoeuvring. On most points of performance, however, the two are remarkably similar.
Activity of Lateral-Line Sense Organs in Swimming Dogfish
Authors: Roberts B. L.
Published: April 2021

The activity of lateral-line sense organs was studied in swimming spinal dogfish by recording from filaments of the lateral-line nerve dissected in an anterior immobile part of the fish, the rest of the fish being free to move. In a non-swimming fish most of the receptors were spontaneously active, discharging at 15–20 impulses/sec. When the part of the body overlying the receptor was flexed, the impulse frequency was either enhanced or depressed, depending on the direction of movement. In swimming spinal dogfish the sense organs discharged in bursts at the same frequency as the swimming rhythm. The lateral-line receptors could provide information which would be useful in locomotory co-ordination, for the burst length, frequency, discharge frequency and number of impulses in the rhythmical discharge could all be correlated with the swimming movements.
Active Transport of α-Aminoisobutyric Acid by the Isolated Midgut of Hyalophora Cecropia
Authors: Nedergaard Signe
Published: April 2021

The α-aminoisobutyric acid flux from lumen to blood of the isolated Cecropia midgut is around 17 μmole/h, while the amino acid flux in the opposite direction is on average 0·3 μmole/h. The amino acid uptake is inhibited by lack of oxygen. It is suggested that the amino acid transport from lumen to blood is an active process. The amino acid uptake is inhibited by short-circuiting the midgut potential, indicating that there is no direct correlation between the active transport of potassium and the uptake of the amino acid by the midgut.
The Water-Holding Mechanism of Sandgrouse Feathers
Authors: Rijke A. M.
Published: April 2021

The barbules of the abdominal feathers of sandgrouse exhibit structural characteristics which are favourable for the uptake of large quantities of water. This feature greatly assists the male of the species in his efforts to bring water to the young. The structural details of feather keratin, peculiar to many fibrous proteins, provide a straightforward explanation of the mechanical transformation of sandgrouse barbules, when wetted, in physico-chemical terms appropriate to macromolecular systems. X-ray analysis of dry and wetted sandgrouse barbules qualitatively support the proposed mechanism of a reversible melting-recrystallization cycle for the barbule keratin.
An Experimental Determination of the Relationship between Lift and Aerodynamic Power in Calliphora Erythrocephala and Phormia Regina
Authors: Wood James
Published: April 2021

Lift and aerodynamic power were calculated for Calliphora and Phormia using assumptions which maximized and minimized the ratio of aerodynamic power to lift.

The ratios of aerodynamic power to lift calculated by these methods, which do not rely on the assumption that steady-state aerodynamics applies to insect flight, are in agreement with results calculated by others using steady-state aerodynamics.
Orientation to Calling Song by Female Crickets, Scapsipedus Marginatus (Gryllidae)
Authors: Murphey R. K. , Zaretsky Malcolm D.
Published: April 2021

Video-tape recordings of the orientation behaviour of female crickets Scapsipedus marginatus in response to the calling song of conspecific males demonstrate that turning and locomotion of the animal toward a target are determined by the sensory information received before the movement is initiated and are unaffected by auditory input received during movement, i.e. the control system is an open-loop type. Sound location comes about through the animals’ ability to turn toward the sound source. The probability of turning in the correct direction is maximal when the sound source lies in the lateral quadrant with respect to the longitudinal body axis, and it is symmetric about the perpendicular to the body axis. The correlation between the angle of the turning response and that of the direction of the sound stimulus is very small. Animals tend to make smaller turns when the target angle is less than 60° than when it is greater than 6o°. Sound which is incident from the posterior direction elicits larger turns than sound which is incident from the anterior direction. Thus, the cricket can tell whether sound is coming from the forward or backward direction and respond accordingly. One-eared animals usually turn toward the intact ear in response to auditory stimulation. The orientation behaviour therefore depends on a comparison of stimuli incident at the two ears. This result contradicts the findings of Regen who claims that one-eared animals can locate a sound source. The leg movements demonstrated by video close-ups of single turns show varying patterns. The pattern postulated by Autrum, however, is not among these.
Flexural Rigidity and Elastic Constant of Cilia
Authors: Baba Shoji A.
Published: April 2021

The flexural rigidity of the large abfrontal cilia of Mytilus has been measured with a flexible glass micro-needle. The same cilium has similar values to the flexural rigidity irrespective of the phases of beat cycle (including the recovery phase) and of the direction of force applied. The values of 3–13 × 10−8 dyne.cm2 have been obtained for the flexural rigidity of compound cilia of various sizes; 2·3 × 10−10 dyne.cm2 for that of the component cilia. The Young’s modulus of the microtubule is estimated to be 5–9 × 1010 dyne/cm2 on the basis that the outer doublet microtubules are tightly connected with one another.
The free Amino acid Pool of the Haemocytes ofCarcinus Maenas(L.)
Authors: Evans P. D.
Published: April 2021

The functions of the blood cells of crustaceans have received little investigation. The majority of the work reported in the literature to date has been concerned with the involvement of the haemocytes in the phenomenon of plasma coagulation. In several crustacean species highly fragile blood cells have been described – ‘Hardy’s explosive corpuscles ‘– which are generally believed to contain substances which can induce plasma coagulation (Hardy, 1892). This is supported by the observation that materials which can decrease, delay, or prevent alterations in the explosive corpuscles have also been found to interfere with plasma coagulation.
An Analysis of the Types of Sensory Unit Present in the PD Proprioceptor of Decapod Crustaceans
Authors: Mill P. J. , Lowe D. A.
Published: April 2021

The PD organs of various decapod crustaceans were stimulated by elongation and relaxation of the strand, and single-unit recordings were made from the different types of sensory unit. The sensory units can all be placed in one or other of three categories : unidirectional movement cells, position cells and intermediate cells. Unidirectional movement cells are large, phasic units which respond either to elongation or relaxation of the strand. Some are pure movement-sensitive units, which reach saturation at very low movement velocities and fire over most or all of the range of movement. Other units show velocity sensitivity and differential range sensitivity in varying degrees. Position cells are small tonic units and are usually maximally sensitive at one end of the range of movement. Their firing pattern is asymmetric in that the frequency of impulses is dependent on the direction of movement by which a given position is achieved. Intermediate cells have large phasic and tonic components which may or may not show a direct relationship to each other. The importance of the detailed information produced by the PD organ is discussed and suggestions made as to how it could be utilized by the central nervous system.
Ventilatory Muscle Activity in Intact Preparations of Aeshnid Dragonfly Larvae
Authors: Pickard R. S. , Mill P. J.
Published: April 2021

The expiratory role of the segmental, respiratory dorso-ventral muscles, and the inspiratory role of the subintestinal muscle, have been confirmed using intact preparations of aeshnid dragonfly larvae. The strain developed by individual respiratory dorso-ventral muscles has been measured. The respiratory dorso-ventral muscles all cease firing simultaneously, about 100 msec before the sterna are fully raised, and do not have any mechanical effect on the sterna after this time. It is suggested that the delay is caused either because the role of these muscles is to lift the sterna past some critical position, and/or because of the inertia of the expiratory current. Periodically the sterna are raised and then lowered slowly in a series of steps, each pause in the lowering coinciding with activity in the respiratory dorso-ventral muscles. This form of ventilation is compared with others previously described. In normal ventilation, and in other types of ventilation, activity in the respiratory dorso-ventral muscles shows a pronounced tendency to begin in the most posterior segments and to continue for longer periods in those segments. Some aspects of the central neural connexions involved in normal ventilation are discussed.
Anal Valve movement and Normal Ventilation in Aeshnid Dragonfly Larvae
Authors: Mill P. J. , Pickard R. S.
Published: April 2021

Anal valve movement and abdominal sternal movement were photographed with a ciné camera during normal ventilation to obtain a correlation between the two parameters. As the sterna are raised (expiration) the anal valve opens to about one third of its maximum. At peak sternal movement the anal valve opens fully and these events mark the transition between expiration and inspiration. The anal valve finally closes towards the end of inspiration. The narrow aperture of the anal valve during expiration, coupled with the increase in pressure in the branchial chamber, causes the expired water to be forced well clear of the anus. Conversely, the wide aperture during inspiration and the small negative pressure in the branchial chamber ensure that water is drawn in from close to the animal, and so there is minimal mixing of expired water with inspired. The relationships between water flow, anal valve movement, branchial chamber pressure, sternal movement, pleural strain, and activity in certain expiratory and inspiratory muscles are discussed.
The Movement of Glucose and Glycine Through the Tissues of Corymorpha Palma Torrey (Coelenterata, Hydrozoa)
Authors: Chapman G. , Pardy R. L.
Published: April 2021

The rate of diffusion of 14C-labelled glucose and glycine across isolated mesogloea and across the mesogloea and cell layers of the large solitary hydroid, Corymorpha was measured. Diffusion coefficients of glucose and glycine in mesogloea were found to be about 16 times lower than their values in water and of the same order as their values in dialysis tubing and Millipore filters,
Electrotonic Conduction in the Optic Nerves of Planorbid Snails
Authors: Patton Marion L. , Rater Stanley B.
Published: April 2021

The conduction of information from the eyes of two basommatophoran snails has been investigated. In the optic nerves of HeHsoma trwolvis and Planorbis corneus a flash of light to the eye produces a procaine-insensitive DC potential that is graded with stimulus intensity and lasts as long as the stimulus. The similar spectral sensitivities, time courses and latencies of the ERG and the slow wave of the optic nerve suggest that the DC response is a decrementally conducted receptor potential. Superimposed on the DC shift are procaine-sensitive oscillations. The oscillations may be either local or propagated regenerative events.
Burst Activity of the Buccal Ganglion of Aplysia Depilans
Authors: Rose R. M.
Published: April 2021

The activity of the buccal ganglion of Aplysia depilans is manifested as regular and sequential bursts of nerve impulses. Regularly firing bursts are seen in the absence of feeding movements. Sequences of bursts lasting for several minutes have been recorded during feeding movements induced by a natural stimulus. A feed-back system has been used to produce bursts in certain other cells synchronous with the regularly firing units. During sequences of bursts there is an alternation of activity between the two groups of neurones. One group is made up of four cells discharging synchronously but within different ranges of frequency. A mathematical model of this activity will be presented in another paper.
The Penetration of Some Non-Polar Molecules in Solution Through the Egg-Shells of Locusta Migratoria Migratorioides and Teleogryllus Commodus
Authors: Browning T. O.
Published: April 2021

The micropylar ends of eggs of Locusta migratoria migratoria were cut off, the tissues were removed, and the empty egg-shells were filled with water or with a solution. The open end was tied off to form a balloon. Balloons containing water were placed in a solution, and those containing solution were placed in water. Balloons containing glucose solution swelled in water and those placed in glucose solution shrank. Little change was observed either in balloons containing urea or in those placed in urea. Results with solutions of malonamide were erratic. Empty egg-shells of Teleogryllus commodus were perfused with radioactive solutions of substances of varying hydrated molecular radii. The smaller molecules (acetamide and urea) passed through the shell into the surrounding liquid more rapidly than the larger ones (glucose and ribose). Shells in which the serosal cuticle was absent were more permeable than those in which it was present. Molecules penetrated living eggs much less readily than they passed out through dead egg-shells. The results are discussed in relation to the permeability of the shells of insect eggs to water and their capacity to restrict the leaching of molecules from the tissues of the egg.
Tissue Culture and Its Contribution to Biology and Medicine
Authors: Fell H. B.
Published: April 2021

I feel deeply honoured at being invited to give the George Bidder Lecture this year. I was asked to talk about tissue culture ; as it happens this is a not inappropriate subject for the present occasion, because Dr Bidder was one of the original benefactors of the Cambridge Research Hospital, which later was renamed the Strangeways Research Laboratory in honour of its founder and became the chief centre for tissue culture in this country. When the Hospital was built in 1911, Dr Bidder thought that it ought to have more land and so with characteristic generosity provided the necessary funds for the purchase of another acre. I cannot tell you how grateful we have been for that extra land as the Laboratory has developed and expanded through the years, and how much we appreciate Dr Bidder’s foresight and kindness.
Input Sources and Properties of Positionsensitive Oculomotor Fibres in the Rock Lobster, Panulirus Interruptus (Randall)
Authors: York B. , Yanagisawa K. , Wiersma C. A. G.
Published: April 2021

Sets of head-up, head-down, eye-up and eye-down motor fibres were studied in the oculomotor nerve of the rock lobster. An eye-withdrawal fibre was also investigated. Apart from the statocyst input, light distribution on the eyes has the strongest influence on the position-sensitive fibres. Weaker optokinetic input from moving targets is also present. Strongly habituating input is obtained from the antennal joints. This input causes orientation of the eye toward the direction in which the antenna points. The same antennule movement in the vertical plane can result in either excitation or inhibition of the head-down fibre, suggesting the presence of two opposing inputs, presumably from the statocysts and basal joint receptors of the antennule. The inputs on to the position-sensitive fibres which indicate body position are such as to stabilize the eye position in space during body movement. The optokinetic and antennal joint inputs are probably involved in tracking and antennal pointing reactions. The eye-withdrawal fibre is stimulated by touch of the head and around the eye, but is inhibited by the excited state.
Eco-Physiological Studies of An Intertidal Crustacean, Pollicipes Polymerus (Cirripedia, Lepadomorpha)
Authors: Fyhn H. J. , Petersen J. A. , Johansen K.
Published: April 2021

Physiological responses to environmental stresses of the intertidal cirriped Pollicipes polymerus have been studied by combined field and laboratory experiments. The body temperature of air-exposed animals is always lower than expected from the heat load. Evaporation from the peduncle is responsible for the heat loss. The rate of water loss by evaporation from the peduncle cuticle is 1·5 μ l/cm2 h mmHg both at 21 and 27°C. The transpiration is proportional to the saturation deficit of the air. The water loss from the capitulum is negligible in comparison to that from the peduncle. The haemolymph osmolality of animals in the field increases during exposure to sunshine and decreases during exposure to rain. The increase in haemolymph osmolality during desiccation is equal to that calculated from the decrease in body water. The water loss during air exposure is adequately replaced during submersion, probably by osmosis. Pollicipes is an osmoconformer but is 5–20 m-osmoles hyperosmotic. It tolerates sea-water dilutions down to about 50 %. The hyperosmolality seems to be balanced by a high internal hydrostatic pressure. An excretory activity is observed. The excretion is isosmotic to the haemolymph and is possibly an ultrafiltrate of the latter. The muscle cells show volume regulation, but free amino acids seem to be unimportant in regulation of intracellular osmolality. The concentration of ninhydrinpositive substances in the muscle tissue is about 200 mm for animals in full strength sea water.