bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct Response of the Crab Carcinus to the Movement of the Sun
Authors: Horridge G. A. 
Published: April 2021

ABSTRACT
One line of evidence points to the conclusion that eye responses should be measurable in a crab, in air, which sees only the movement of the sun in a clear sky. It has been shown in the previous paper, as an extension of earlier work with slowly moving striped drums, that eyestalk movements follow a single light in a dark room when the light is moved with low angular velocities round the crab in the range 10–20°/hr. For horizontal movements which subtend angles of 0·02–1·0° at the crab’s eye, at a lamp velocity of 0·01°/sec., the horizontal eye movement is 20–50% of the light’s movement. The light used gave an illumination of 0·05 lux on a surface in the position of the crab’s eye. These figures remove any doubt that the crab is able to see the movement of the sun directly. The movement of the full moon, with a maximum illumination of 0·24 lux on the earth’s surface, must also be seen by the crab, and possibly some of the brighter stars are also seen directly. Whether the crab responds to these moving lights will depend, not only on whether it sees them, but also on whether there are stationary contrasting objects in the visual field. If the eye begins to follow an isolated moving stimulus, other contrasting objects will move in the opposite direction over the eye, and this will at once diminish the response by an opposite stimulus. Therefore, to make sure of recording a maximum response to celestial movements the animal should see as little as possible besides the object of interest.
The Nervous Control of Ventilation in Dragonfly Larvae
Authors: Mill P. J. , Hughes G. M. 
Published: April 2021

ABSTRACT
Ventilatory movements of the sterna are effected by the paired segmental respiratory dorso-ventral muscles in abdominal segments 4-9 (expiration) and by the natural elasticity of the cuticle aided by two transverse abdominal muscles, the diaphragm and the sub-intestinal transverse muscle (inspiration). The former are innervated by the second segmental nerves, the latter by median nerves. Rhythmic motor discharges were recorded in the nerves to both expiratory and inspiratory muscles. Expiratory bursts consist of a single unit, the firing frequency of which increases during the burst and then normally decreases slightly at the end of the burst. Inspiratory bursts show a rather irregular discharge of the unit(s) within them, the overall frequency of which increases slightly during the first half of the burst. Each spike in the expiratory burst is accompanied by a muscle action potential in the respiratory dorso-ventral muscle it innervates. With increase in frequency of the motor unit facilitation of the muscle action potentials occurs. No such facilitation has been observed in the inspiratory muscles. The mean firing frequency of the expiratory unit increases steadily with increase in burst duration over the normal range of respiratory frequency and a similar minimum interval is attained irrespective of the duration of the burst. Expiratory bursts in second roots of the same ganglion are synchronous and may show a 1:1 relationship. Expiratory bursts start first in posterior segments and the eighth ganglion presumably contains a pacemaker. The duration and number of impulses per burst decrease from behind forwards. However, the expiratory unit reaches its maximum frequency at about the same time in all segments. Stimulation of a first segmental nerve root in the posterior region of the abdomen in an inter-expiratory period causes expiratory bursts to appear in the second roots and consequently re-sets the respiratory rhythm. The inspiratory neurones start to fire very shortly after cessation of the expiratory burst and are closely coupled with the latter. Rhythmic bursts containing many units were recorded in the isolated ventral nerve cord, usually after application of carbon dioxide to the preparation.
Patterns of Ventilation in Dragonfly Larvae
Authors: Hughes G. M. , Mill P. J. 
Published: April 2021

ABSTRACT
A study has been made of the patterns of ventilation in three genera of anisopteran dragonfly larvae by recording simultaneously the pressure changes in the branchial chamber and the dorso-ventral movements of the abdomen. The three main types of ventilation described by Tonner have been confirmed and the characteristic pressure changes during normal, gulping, and chewing ventilation are described. During normal ventilation there is a positive pressure phase of about 4 cm. water followed by a brief negative phase of 12 cm. water. The main expiratory phase is produced by the respiratory dorso-ventral muscles which are found in abdominal segments 4–9. Inspiration, which closely follows expiration, results from the elastic properties of the exoskeleton together with the activity of the two transverse muscles. One of these, lying at the anterior end of the fifth abdominal segment, forms the so-called diaphragm and divides the abdomen into two functional cavities. Gulping ventilation is characterized by a maintained pressure of 20–40 cm. water during which there may be fluctuations associated with the chewing movements, which are mainly due to the intrinsic musculature of the colon and rectum. Despite some differences in detail the main patterns of ventilation are very similar in Aeshna, Anax and Libellula.
Analysis of Formed Bodies in Urine Removed from the Crayfish Antennal Gland By Micropuncture
Authors: Riegel J. A. 
Published: April 2021

ABSTRACT
Two kinds of formed bodies are present in the urine of the crayfish: spheroids, which appear to be produced by the coelomosac cells and appear in all parts of the antennal gland except the bladder; and vesicles, which are produced by the cells of the labyrinth and are found only in the labyrinth. Chemical analysis of the formed bodies show them to contain peptides and amino acids, especially in the more distal portions of the antennal gland. It is suggested that the spheroids also contain proteins, but that this material is inseparable from their structure. The significance of the formed bodies in the excretion process of the crayfish is discussed.
The Pleated Surface of the Undischarged Thread of A Nematocyst and Its Simulation by Models
Authors: Skaer R. J. , Picken L. E. R. 
Published: April 2021

ABSTRACT
The complex appearance in electron micrographs of sections, both transverse and longitudinal, of the undischarged thread of a nematocyst—the large holotrichous isorhiza of Corynactis viridis Allman—is compatible with the pleating of a tubular thread to form a triple-screw surface (Skaer & Picken, 1965). This interpretation of the sections was facilitated by a study of the properties of folded paper models, and by the construction of a three-dimensional wax model following, essentially, the method of His (1887), but with the difference that sections modelled in wax were serial electron micrographs of ultrathin transverse sections (Picken & Skaer, 1966). This wax model being fragile and opaque, it was subsequently cast in more robust and translucent Araldite resin by a cire perdu method.
The Physiology of A Lepidopteran Muscle Receptor
Authors: Weevers R. De G. 
Published: April 2021

ABSTRACT
When a single MRO of a caterpillar is stretched at least 32 motor units show clear reflex changes in activity. The great majority of muscles are excited., and the latency of the reflex differs only slightly from one muscle to another. The response has both tonic and phasic components which reflect more or less faithfully the magnitudes of the same components in the sensory discharge. Muscles are affected on the contralateral side of the stimulated segment and on the ipsilateral side of adjacent segments. The reflex fields of neighbouring receptors therefore overlap; spatial facilitation produces a disproportionate increase in the overall response when two receptors are stimulated simultaneously. The reflex pathway for muscles innervated by nerve 2 is shown to involve synaptic connexions in the ganglion of the segment anterior to the stimulated receptor and responding muscles. The muscles most strongly excited are those which he functionally in parallel with a stretched sense organ. It is concluded that a major function of the caterpillar MRO is to mediate a negative feedback reflex tending to stabilize bodily position independent of load.
The Evaporation of Water from Helix Aspersa
Authors: Machin John 
Published: April 2021

ABSTRACT
Data is presented which suggest that inactive specimens of Helix aspersa are able to regulate evaporative water loss from the mantle. Evaporation is reduced following the cessation of glandular extrusion, by the concentration of solutes in partially dehydrated superficial mucus. Methods are described for determining vapour pressure gradients across living and freshly killed mantle tissue and for calculating permeabilities. Osmotic permeability measurements using isolated and intact body wall were made. The permeability of regulating mantle tissue was 0·039 mg./cm.2/hr. per mm. Hg vapour pressure difference. Living body wall and freshly killed mantle were at least forty times more permeable to water. Low permeability seems to be a unique property of living mantle tissue.
Measurements of Glucose and Amino Acid Concentrations, Temperature and PH in the Habitat of Polymorphus Minutus (Acanthocephala) in the Intestine of Domestic Ducks
Authors: Crompton D. W. T. 
Published: April 2021

ABSTRACT
Measurements have been made on the glucose and amino acid concentrations, temperature and pH in the lumen of the small intestine of the domestic duck in the region inhabited by the acanthocephalan parasite, Polymorphus minutus. The glucose concentration was found to vary from 23 mg./ml. to no detectable glucose, with an average value of about 5·7 mg./ml. for the twenty-four ducks examined. Sixteen amino acids were detected by qualitative and quantitative methods. The temperature in the parasite’s habitat is the same as the other published deep body temperatures of domestic ducks. The pH appears to be about 7·5.
Burrowing in Mercenaria Mercenaria (L.) (Bivalvia, Veneridae)
Authors: Ansell A. D. , Trueman E. R. 
Published: April 2021

ABSTRACT
Burrowing of the bivalve Mercenaria mercenaria has been re-examined using modem recording techniques. Burrowing activity consists of a series of movements, repeated cyclically termed the ‘digging cycle’, involving extension of the foot, closure of the siphons, adduction of the shell valves and retraction of the foot, Final position in the sand is only reached after many digging cycles, constituting a digging period. Closure of the siphons and apposition of the mantle margins temporarily seals the mantle cavity to form a pressure chamber through which forces produced by adduction can be transmitted to act elsewhere. Adduction causes dilation of the distal regions of the foot, aiding pedal anchorage, and ejection of water from the mantle cavity loosens the sand ventrally and laterally. Downward movement is by the passive dropping of the heavy shell into the fluid cavity formed at adduction, and by active movement caused by contraction of the retractor muscles pulling the shell downwards on to the anchored foot. The strength of pedal retraction is 5-6 g. in an animal of 21 g. wt. in water. With the shell completely covered by sand the opening moment of the ligament is shown to be too small to effect complete opening of the valves, and under these circumstances pressures generated by withdrawal of the foot and siphons in a secondary phase of siphonal movements supplement the action of the ligament. Burrowing movements in Mercenaria are compared with those of Tellina, Donax, Macoma, Cardium and Ensis.
The Effect of Hypoxia Upon the Partial Pressure of Gases in the Blood and Water Afferent and Efferent to the Gills of Rainbow Trout
Authors: Holeton G. F. , Randall D. J. 
Published: April 2021

ABSTRACT
The rate of oxygen uptake by rainbow trout does not alter during progressive deoxygenation of the environment. Blood lactate, however, shows a significant increase, indicating an increase in anaerobic metabolism during hypoxia. The percentage utilization of oxygen from the water decreased from 55 % to approximately 20% during hypoxia and was associated with a 13-fold increase in ventilation volume. The arterial blood of a trout resting in aerated water was 95–100% saturated: the was 122 mm. Hg and the was 1−1·5 mm. Hg. The venous blood of a resting trout was 70 % saturated, had a of 35 mm. Hg and a of 2·5 mm. Hg. During hypoxia the percentage saturation of the arterial blood decreased to 37 % and that of the venous blood to 3 %. The in the arterial blood was 10 mm. Hg ; in the venous blood, 6 mm. Hg. The in the arterial blood was 3·5−4 mm. Hg; in the venous blood, 4·5−5·00 mm. Hg respectively. The ability of the fish to withstand hypoxia was related to the oxygen capacity of the blood, which was on average 9 vol. %. The red blood cells swelled during hypoxia, the hematocrit increased, but the red cell count did not alter. Blood pH was 7·7, falling to 7·4 during hypoxia. Cardiac output did not change during progressive hypoxia in the water, stroke volume increased to offset the decrease in heart rate.
Flight in Drosophila
Authors: Vogel Steven 
Published: April 2021

ABSTRACT
In tethered flight in a wind tunnel fruit-flies adjust lift and thrust by shifting the horizontal component of the lower extreme wing position. The upper extreme wing position is nearly constant. Stroke angle and stroke plane are fully interdependent parameters. Angle of attack varies along the length of the wing; no length-wise twisting occurs. Angle of attack varies with flying speed ; pitch is unchanged as speed is increased. These characteristics suggest that the flight machinery of fruit-flies is considerably simpler than that of larger flying animals.
Discharge Patterns of Neurones Supplying Tonic Abdominal Flexor Muscles in the Crayfish
Authors: Evoy William H. , Kennedy Donald , Wilson Donald M. 
Published: April 2021

ABSTRACT
The discharge patterns of tonic flexor motoneurones in the crayfish abdomen have been investigated by simultaneous recording from several nerve roots. The five flexor motoneurones supplying each segment are serially homologous, smaller units have higher discharge frequencies, and the excitability of a given unit is generally higher in more caudal ganglia. Even the smallest axons are capable of generating substantial muscle tension at their spontaneous discharge frequencies. Tension development is extremely tonic. Single motor impulses are without effect, latencies are long, and the frequency/tension relation is steep. The inhibitory axon to each flexor discharges during ‘extension’ reflexes, but has no visible effect upon relaxation time, or upon the response to subsequent excitation. Inhibitory impulses do not relax previously unexcited muscle. Phase histograms for the discharge of pairs of homologous or non-homologous efferent axons across a single ganglion, within the same root, and between adjacent ganglia have revealed several coupling mechanisms. One is mediated by short timeconstant electrotonic junctions between bilaterally paired inhibitory axons. The second involves weaker, more generalized interactions of longer time-constant between non-homologous axons. The third is brought about by common presynaptic sources of excitation. Inputs tend to be common for homologues in adjacent ganglia rather than for non-homologues in a single ganglion, a finding consistent with the selectivity shown by central interneurones in their effects upon motoneurones.
Slow Activity in the Nervous System of the Earthworm, Lumbricus Terrestris
Authors: Roberts M. B. V. 
Published: April 2021

ABSTRACT
Three thresholds are demonstrated in the first segmental nerve and two (sometimes three) in the second and third segmental nerves together. Slow potentials recorded from the ventral nerve cord consist of several peaks. The first peak is composed of three spikes which make their appearance at different thresholds. Transmission of at least some of the slow potentials is decremental. Transmission speeds in the nerve cord and segmental nerves range from 0·4 to 0·6 m./sec. Action potentials in the longitudinal muscle are recorded in response to slow potentials in the nerve cord. Two slow reflexes, one involving elongation, the other longitudinal contraction, are described. The latter has the lower threshold with peripheral stimulation. Slow activity in the nervous system is discussed in relation to reflex activity of the earthworm and the neurone anatomy of the nerve cord and segmental nerves.
The Mechanism of Lung Ventilation in the Tortoise Testudo Graeca Linne
Authors: Gans C. , Hughes G. M. 
Published: April 2021

ABSTRACT
An account is given of the gross structure of the respiratory system and of the principal muscles involved in ventilation of the tortoise, Testudo graeca. The mechanism of ventilation was investigated by electrophysiological methods. Cannulae inserted into the lung through holes drilled in the shell recorded pressure changes during the cycle of ventilation and simultaneous recordings were made of the forelimbs movements. The pressure changes were triphasic in form, consisting of an initial increase in pressure followed by a fall to a level of 7 cm. water below atmospheric, and again returned to the atmospheric level or usually slightly above. During the pause between individual ventilation cycles, any overshoot gradually declined to the base-line. Electromyograms showed that all phases of the respiratory cycle were active. The increase in pressure was accompanied by activity in the transversus abdominis and in the pectoralis muscle which draws the shoulder girdle back into the shell. These activities increase the pressure in the peritoneal cavity, which is transmitted to the lung. During the opposite phase of the cycle, the obliquus abdominis and serratus major muscles are active. This increases the volume of the peritoneal cavity and leads to the reduction in intrapulmonary pressure below atmospheric. Activity recorded from the opener and closer muscles of the glottis showed that the glottis is dilated during the first two parts of the cycle but not during the final recompression phase. The respiratory rhythm does not appear to be composed of brief periods of ventilation activity followed by prolonged pauses, as supposed by many authors. These differences may relate to the species investigated. No evidence was found for significant differences in pressure between the right and left lungs or between the anterior and posterior chambers of the lung on one side. It is concluded that the mechanism producing ventilation in the tortoise takes advantage of the only possible way of changing the volume of the thoracico-peritoneal cavity, namely by altering the position of the limb flanks. Both expiratory and inspiratory movements are active.
Mechanisms for the Production of the Motor Output Pattern in Flying Locusts
Authors: Waldron Ingrid 
Published: April 2021

ABSTRACT
The normal flight pattern consists of alternating bursts of activity in the elevator and depressor motor neurons. However, when sensory input depresses elevator activity, rhythmic bursts of activity in the depressor motor neurons may continue even after all elevator motor neuron activity has apparently ceased. Thus interactions between the antagonistic motor neurons apparently are not necessary for the production of the rhythmic bursts. The proposed mechanism for producing these rhythmic bursts depends on the excitatory interactions among the synergistic motor neurons. Alternative or supplementary explanations for the data seem to be possible only if interneurons participate in the generation of the flight pattern. During flight initiation, when there is a burst of activity in several depressor motor units simultaneously there usually is a pause in the on-going elevator activity ; often the normal flight pattern begins at this time. This reciprocal relationship of activity in the antagonists suggests inhibitory coupling between antagonistic motor neurons or between interneurons which may drive them. This coupling may be responsible for the alternation of the bursts of activity in the antagonists during normal flight. There is no evidence for greater co-ordination within a thoracic ganglion than between ganglia. Some activity in the abdominal C.N.S. is also well co-ordinated with the flight pattern. Thus the anatomical separation into ganglia does not correspond to any interruption of the functional integration of the flight system.
Neural Mechanism by Which Controlling Inputs Influence Motor Output in the Flying Locust
Authors: Waldron Ingrid 
Published: April 2021

ABSTRACT
The central nervous system of the flying locust generates a pattern of alternating bursts of impulses in the elevator and depressor motor neurons (Wilson, 1961). The mechanism by which controlling inputs modify this output pattern is analysed in this paper. During roll turns and other flight manoeuvres the average number of impulses per burst (average burst length) changes in certain motor neurons. Changes in average burst length develop slowly, over tens of wingbeat cycles, even in response to the abrupt changes in input which result from electrical stimulation of sensory nerves. In addition to the slow changes in average burst length which are elicited by controlling inputs, more rapid changes in burst length sometimes occur. During this rapid variation a longer burst is usually followed by a shorter burst, probably because the motor neuron is less excitable after a longer burst of activity. Burst length varies independently in different motor neurons. Both findings suggest that much of the rapid variation in burst length is due to changes occurring within the individual motor neurons, and is not a response to rapid changes in controlling inputs. Under all conditions, changes in the number of impulses per burst are correlated with small changes in the relative timing of the burst; the longer bursts produced by a motor neuron begin slightly earlier in the wingbeat cycle. This implies that the factors which cause variation in the length of the bursts are also responsible for producing the variation in the timing of the bursts. All of the observations can be explained on one assumption: that the only effect of controlling inputs is to cause slow changes in the ‘average excitation’ of individual motor neurons. Thus sensory and central control of the flight pattern generating system appears to be slow control over the average performance, rather than fast control over performance in a particular cycle.