bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conduction Along the Ventral Nerve Cord of A Hemichordate Worm
Authors: Pickens Peter E. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.
An Experimental Determination of the Relationship between Lift and Aerodynamic Power in Calliphora Erythrocephala and Phormia Regina
Authors: Wood James 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACTThe 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

ABSTRACTThe 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.