bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dimensions and Sensitivities of Semicircular Canals
Authors: Ten Kate J. H. , Van Barneveld H. H. , Kuiper J. W. 
Published: April 2021

ABSTRACT
The dimensions of the semicircular canals of pike can be expressed as allometric functions of the body length L. The equal sensitivity of pike of different sizes to rotatory stimulation can be explained as a quadratic bending of the cupula. In the pike the sensitivity is of the same order of magnitude for the vertical and horizontal semicircular canals. In the pike the growth rate of the volumes of duct and ampulla is the same for the horizontal semicircular canal and for the posterior semicircular canal. The special growth rate of the dimensions of the horizontal semicircular canal of the ray can be explained by a quadratic bending of the cupula. For equally large cupulae the sensitivity of the horizontal semicircular canal is of the same order of magnitude for twenty-three mammals, fourteen birds and one reptile as it is for the pike. Within the limits of error the ‘growth rate’ of the diameter of the narrow duct is the same in mammals as in the pike. At the same body mass the absolute value of the diameter of the narrow duct is smaller in mammals than in the pike by a factor of 1·69. For a body mass of 1 kg the value of the enclosed area of the horizontal semicircular canal is 6 times smaller in mammals than in pike. The model of the overcritically damped oscillator for the semicircular canal remains valid during growth if a quadratic bending of the cupula is assumed.
Studies of Cardio-Regulation in the Cockroach, Periplaneta Americana
Authors: Miller T. , Usherwood P. N. R. 
Published: April 2021

ABSTRACT
The heart of Periplaneta americana is segmentally innervated from the central nervous system by three types of neurone. Two of these types of neurones are neurosecretory; one type contains large granules, the other small granules. The segmental nerves are paired structures which join paired lateral cardiac nerve cords. Both types of neurosecretory neurone liberate their contents in the lateral cardiac nerve cords. The neurones with the small granules also synapse with the myocardium as well as with intrinsic cardiac neurones in the lateral cardiac nerve cords. The third type of neurone from the central nervous system is an ordinary efferent neurone and it synapses with the cardiac ganglion cells. A heart chamber is associated with about six cardiac ganglion cells, three on either side. These send processes up and down the lateral cardiac nerve cord and make synaptic contact with the myocardium. The myocardium is multiterminally and polyneuronally innervated, and electrical coupling between muscle fibres appears to be the rule. The fibres are spontaneously active and generate spike-like electrically excited responses. The timing of the electrically excited responses is influenced by the input from the cardiac ganglion cells which evoke a burst of synaptic potentials during diastole. Control of the cockroach heart appears to be organized on three levels. The basic rhythm is myogenic. The timing of the contractions is influenced by inputs from the intrinsic cardiac ganglion cells possibly via a feedback mechanism involving the contractions of the heart muscle. Finally, the activities of the heart muscle and the cardiac ganglion cells are influenced by inputs from the central nervous system.
Mid-Brain Responses of the Auditory and Somatic Vibration Systems in Snakes
Authors: Hartline Peter H. 
Published: April 2021

ABSTRACT
Evoked slow potentials were recorded extracellularly from the mid-brains of snakes of the genus Crotalus. For the auditory and somatic systems, amplitude, latency, and duration of responses were studied as the parameters of intensity, frequency, and rise time of sinusoidal vibratory or click stimuli were varied. Recovery curves were constructed for paired stimuli and for trains. Effects of body temperature on frequency-response threshold curves were determined. Results were verified for species of the families Boidae and Colubridae. Intensity-amplitude curves increase logarithmically for c. 20 dB above threshold and then reach a plateau for the auditory system. These curves are generally increasing over a 40 dB range in the somatic system. Latency decreases monotonically with increasing intensity; it is independent of frequency for the auditory system but depends on frequency for the somatic system. Differences in shape of intensity-amplitude curves for different frequencies lead to the hypothesis that there are auditory units with different frequency-response curves. This finding is relevant to the study of the evolution of audition. Differences in intensity-amplitude curves for the somatic system and differences in latencies for different frequencies suggest that several types of somatic vibration receptors contribute to the central response. Increase in body temperature causes increase in the frequency of greatest sensitivity for the auditory system, and increases sensitivity by 1−3 dB per°C. Higher frequencies are affected more than lower frequencies. The somatic system sensitivity is increased by c. 1·5 dB per°C, except at the extremes of the frequency curve. These findings emphasize the importance of studying effects of temperature on the central nervous systems of cold-blooded vertebrates. Of relevance to the biology of snakes is the observation that snakes are not well suited, at the mid-brain level, for rapid analysis of sequential vibratory events. A principle of general biological significance supported by comparison of temporal characteristics of mid-brain responses of snakes and other animals is that latency and recovery are related to auditory specialization rather than to phylogeny.
The Different Connections and Motor Outputs of Lateral and Medial Giant Fibres in the Crayfish
Authors: Larimer James L. , Eggleston Alan C. , Masukawa Leona M. , Kennedy Donald 
Published: April 2021

ABSTRACT
High-speed cinematography was used to analyse the abdominal movements of crayfish in response to separate stimulation of medial and lateral giant axons. These films showed that the medial giant fibres command complete abdominal flexions with little flaring of the tail appendages. The lateral giants, in contrast, evoked a relatively weak flexion of the middle abdominal segments, accompanied by promotion of the exopodites of the uropods. An examination of the muscles activated by the two types of giant fibres shows that differences in the connexions between the giant fibres and specific motor neurones can account for the behavioural differences observed. The output of the giant fibres was determined in the sixth abdominal ganglion, where their differential effects are most pronounced. The medial giants activate motor neurones whose axons emerge from root 6 of the sixth ganglion. The lateral giants activate motor neurones whose axons emerge via roots 2 and 3, as well as those emerging via root 6. The larger motor neurones associated with the giant axons in the sixth root of the sixth ganglion have been mapped by Procion Yellow injection, and the terminations of the central giant axons in the sixth ganglion have also been determined. The connexions revealed by this technique are consistent with the physiological findings. The evidence suggests that root 6 of the sixth ganglion is homologous with root 3 of the more anterior ganglia. However, the giant motor neurone of the sixth ganglion has not been identified. The medial and lateral giant fibres, and perhaps other specific ‘command’ interneurones, can thus drive specific ensembles of phasic motor neurones to provide a range of stereotyped quick movements. In this respect the organization of the phasic system of interneurones and motor neurones resembles that in the tonic system.
The Locomotion of the Cockroach Periplaneta Americana
Authors: Delcomyn Fred 
Published: April 2021

ABSTRACT
The locomotion of free, intact cockroaches, Periplaneta americana, was studied with the aid of high speed motion pictures. The insects used a single gait, alternating triangle, at all speeds of locomotion (5–80 cm/s) except the very lowest ones (below 5 cm/s). Both forward (protraction) and rearward (retraction) movements of the legs relative to the body decreased in duration as the insect’s rate of forward progression increased, but at different rates. In addition, protraction was usually shorter for the two middle legs than for the remaining four. The ratio of protraction to retraction increased as the locomotor rate increased. The rate of change of this ratio was the same for each of the legs. Phase relationships between adjacent ipsilateral legs were constant at about 0·5 at all walking speeds above about 5 cm/s. Phase between legs in a single segment (i.e. contralateral pairs) was constant at about 0·5 at all speeds. The locomotion of Periplaneta was compared to that of other insects. Despite the differences, a single mechanism could account for walking in each.
The Effect of Limb Amputation On Locomotion in the Cockroach Periplaneta Americana
Authors: Delcomyn Fred 
Published: April 2021

ABSTRACT
The effects of amputating parts of legs on walking in the cockroach Periplaneta americana were studied with the aid of high-speed motion pictures. Amputation of one or two legs at the femoro-tibial joint, leaving the femur to touch the ground and thus provide support during walking, had very little effect on the timing of movements of ipsilateral or contralateral leg pairs, so that gait was constant at nearly all speeds of locomotion. The cycle of forward (protraction) and rearward (retraction) movements of individual legs was also little affected by the amputations. Amputation of combinations of two legs at the trochantero-femoral joint, leaving the animal without the support of the amputated legs, had no effect on the timing of movements of contralateral leg pairs, but had a strong effect on timing between ipsilateral ones, such that gait changed as a function of the speed of locomotion. Except for a general depression in most cases, the ratio of protraction to retraction for each leg at any given walking speed was unchanged. On the basis of these results it is suggested that the timing of leg movements is strongly influenced by feedback from peripheral receptors, while the cycle of protraction and retraction in each leg is largely under central control. A model of this control based on sinusoidal activation and inhibition of muscles of protraction and retraction is presented and discussed.
The Effect of Calcium On Sodium Influx and Loss in Gammarus (Amphipoda)
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
In Gammarus pulex and G. duebeni sodium influx from sodium chloride solutions and sodium loss into de-ionized water were not affected in a consistent manner by the presence of calcium ions at concentrations up to about 2 mM/1. Sodium influx in G. pulex was depressed by the addition of 2–10 mM/1. calcium. Sodium influx in G. zaddachi was stimulated by the addition of 2–4 mM/1. calcium chloride but depressed by the addition of 20–53 mM/1. calcium chloride.
The Phasic and Tonic Contraction in the Longitudinal Muscle of the Earthworm
Authors: Tashiro N. , Yamamoto T. 
Published: April 2021

ABSTRACT
In extension of preceding studies on the mechanical properties of the longitudinal muscle fibres of the earthworm, the phasic and tonic contractions were analysed under various conditions. The phasic contractions appeared on the tonic contraction which was maintained at a steady level by repetitive stimulation, and the tonic contraction decayed very slowly after cessation of stimulation. The length-tension curve indicated that the phasic and tonic contractions were both affected similarly by changing the muscle length. The mechanical ‘active state’ was investigated during the phasic and tonic contractions by means of the quick-release method. During the phasic contraction the ability to redevelop the tension was observed. During the early phase of the tonic contraction the muscle was in the ‘active state‘, but the tonic contraction continued even after the tension redevelopment had nearly ceased. The tonic contraction was absent when the temperature was raised to about 30 °C. 5-Hydroxytryptamine (2·5 × 10−6 M) decreased the tonic more than the phasic contraction. The tonic contraction disappeared completely in the presence of acetylcholine (5·5 × 10−4 M), while the phasic contraction was reduced but not abolished, λ-aminobutyric acid (10−8 to 5 × 10−4 M) had no effect on the contractions. Transition-metal ions suppressed mainly the phasic contraction in the order of Mn2+&gt; Co2+ &gt; Ni2+. The decrease in the phasic contraction was proportional to the logarithm of concentration of added divalent cations. The tonic contraction was also reduced but at higher concentration than the phasic contraction. It is postulated that, by depolarization produced by electrical stimulation or by acetylcholine, calcium ions are released from the plasma membrane and also from the sarcoplasmic reticulum. The phasic contraction might be generated mainly by calcium ions released from the membrane, and the tonic contraction might be caused mainly by calcium ions released from the sarcoplasmic reticulum.
Further Studies on Synaptic Transmission in Insects
Authors: Callec J. J. , Guillet J. C. , Pichon Y. , Boistel J. 
Published: April 2021

ABSTRACT
Some integrative properties of the chemical synapses between the sensory cereal afferent fibres and a giant axon are studied at the unitary level by external recording. Unitary monosynaptic EPSPs are related to cereal receptor activity, one presynaptic spike inducing one EPSP. Unitary IPSPs are not directly related to cereal activity. They seem to originate within a ganglion. Many receptors make synaptic contacts with a given giant axon. When a single receptor is strongly stimulated, the summation of elementary induced EPSPs gives a postsynaptic depolarization which is not able to reach the threshold. The simultaneous stimulation of several receptors provides a considerable amount of postsynaptic depolarization, thus triggering one or two spikes, rarely more. The postsynaptic responses appear to be more or less different according to the afferent firing pattern: phasic, phasic-tonic and tonic. Some factors modulate these schemes: (a) Potentiation, which occurs only with phasic patterns, thus increasing their postsynaptic effect, is followed by a longer component of depression. (b) Limiting factors, such as fatigue phenomenon, are thought to be essentially related to depletion of an available transmitter. Synchronous electrical stimulation induces a monosynaptic response, later followed by a complex polysynaptic phenomenon. These responses decrease with repetitive stimulation, but the former is far less labile than the latter. These studies seem to indicate that a giant interneurone in the cockroach fires only in special conditions, namely when a strong mechanical stimulation occurs after a noticeable period of rest. This spike is then rapidly conducted to higher centres without relay.
Neural Redundancy and Regularity of Swimming Beats in Scyphozoan Medusae
Authors: Lerner Jacqueline , Mellen Suzanne A. , Waldron Ingrid , Factor Robert M. 
Published: April 2021

ABSTRACT
Despite the apparent symmetry of jellyfish the eight ganglia do not all have equal levels of activity in initiating swimming beats. Differences in activity level persist over several hours, both in the intact jellyfish and after isolation of the individual ganglia. Horridge has proposed a specific model of how the regularity of the swimming beat should be increased by the redundancy of pacemakers (one in each ganglion). Our data are quantitatively incompatible with this model. However, this incompatibility may be due more to the impossibility of maintaining comparable levels of sensory input at different stages of the test than to deficiencies in the model. Regular beating in the whole jellyfish is probably due to both redundancy of pacemakers and more regular functioning of individual pacemakers when they receive greater excitatory input.
Sound Reception in the Bush Cricket Metrioptera Brachyptera (L.) (Orthoptera, Tettigonioidea)
Authors: Lewis D. B. , Pye J. D. , Howse P. E. 
Published: April 2021

ABSTRACT
This paper presents an analysis of the impulse patterns in the tympanal nerve of Metrioptera branchyptera (L) in response to a variety of insect song stimuli in order to determine the relationship of the syllable rate and of intrasyllabic features to the action-potential sequence. Recordings of the proclamation songs of M. brachyptera and Chorthippus parallelus (Zetterstedt) made with a conventional audio-frequency tape-recorder and with a high-frequency tape-recorder have been analysed. The song of M. brachyptera is composed of five syllables/chirp, corresponding to the opening and closing strokes of the tegmina; each syllable consists of twenty-five to forty intrasyllabic spikes which correspond to individual tooth strikes. The main sound energy lies between 15 and 85 kHz centred roughly on 25 and 67 kHz in the closing syllables and on 45 and 65 kHz in the weaker opening syllables. The song of C. parallelus consists of single chirps with loud downstroke syllables and softer upstroke syllables. The main sound energy lies between 7 kHz and 80 kHz, centred on four bands at about 10–15 kHz, 22–25 kHz, 37–40 kHz and 60–70 kHz. Live song, audio-frequency recordings and high-frequency recordings of M. brachyptera song were used as stimuli for the tympanal nerve preparation. The action potentials produced in response to the live or to the high-frequency recording of the song show a high correlation with the intrasyllabic spikes, though not in response to the audio-frequency recording. Inadequate reproduction may therefore be an important potential source of error. By presenting the high-frequency recording through a band-pass filter various degrees of distortion of the song are achieved, and in this way it is shown that the important features of the proclamation song of the species are the intrasyllabic spikes. The action potentials recorded from the tympanal nerve of M. brachyptera in response to the live song, audio-frequency recordings and high-frequency recordings of C. parallelus confirm the importance of the intrasyllabic spikes, and show that no ‘timing’ of the tympanal organ to the species song occurs.
The Body Temperature of Tenebrionid Beetles in the Namib Desert of Southern Africa
Authors: Edney E. B. 
Published: April 2021

ABSTRACT
In direct sunshine the abdomen of living Onymacris brincki, which is covered by white elytra, was 3 − 4 °C cooler than its thorax, while in the same conditions the abdomen and thorax of O. rugatipennis, which is an entirely black beetle, had the same temperature. Since similar effects were observed in dead beetles, the warmer thorax was not due to muscular activity. When the white elytra of brincki were covered with carbon black, its abdominal temperature rose to equal that of rugatipennis. Models, made of pieces of black and white elytra, showed similar effects. The smaller species Stenocara eburnea (with white elytra) showed a smaller and less consistent temperature depression when compared with the similar-sized species S. depressa (which is black). Abdomens of O. rugatipennis, O. laeviceps and Physostema cribripes (all large black beetles) were from 3 − 5 °C warmer than O. brincki, but showed no consistent difference among themselves. When O. rugatipennis was oriented head-on to the sun in its natural environment its thorax was about 4 °C cooler than when its long axis was normal to the sun’s rays. Beetles exposed to sunshine were 12 − 15 °C warmer than they were in the shade. When transferred from one to the other, the greater part of temperature equilibration occurred in about 2 min and equilibration was complete in about 4 min. Observation suggested that beetles thermoregulate by moving between sunshine and shade. Measurements showed that a beetle exposed to alternating periods of 10 sec in sunshine and 30 sec in shade reached a steady temperature of about 33 °C, while the reverse conditions (10 sec in the shade and 30 sec in sunshine) led to a temperature of about 38 °C. In continuous alternations thoracic temperatures remained const within about i °C. Laboratory experiments in which the angle of incidence of the sun’s rays was varied through 180° confirmed the field results and showed that white elytra lower the abdominal temperature of living and dead beetles. Upper lethal temperatures for 30 min in saturated air varied from 50 °C for the desert tenebrionid Onymacris plana to 42-5 °C for the mesic species Trigonopus capicola. In general, upper lethal temperatures correlated well with habitat and habit. Making certain assumptions, analysis of the heat balance of beetles during one exposure in sunshine suggests that the difference between the white elytra of brincki and the black ones of rugatipennis as regards the amount of short-wave radiation reflected is 0-227 cm− 2 min−1, and further, that the reflectivities of the two surfaces are 79% and 38% respectively. The selective advantage of white elytra probably has little to do with heat balance ; the vivid contrast between white and black suggests that the pattern may be aposematic.
Gas Tensions in the lungs and Major Blood Vessels of the Urodele Amphibian, Amphiuma Tridactylum
Authors: Toews Daniel P. , Shelton G. , Randall D. J. 
Published: April 2021

ABSTRACT
Oxygen and carbon dioxide tensions were determined in the lungs and in blood from the dorsal aorta, pulmonary vein, pulmonary artery and inferior vena cava in the intact, free swimming, Amphiuma. At 15°C this animal was submerged for a large part of the time and surfaced briefly to breathe at variable time intervals, the mean period being 45 min. Oxygen tensions in the lungs and in all blood vessels oscillated with the breathing cycles, falling gradually during the period of submersion and rising rapidly after the animal breathed. The absolute level of oxygen tension did not appear to constitute the effective signal beginning or ending a series of breathing movements. A small oxygen gradient existed between lungs and blood in the pulmonary vein immediately after a breath. The gradient increased in size as an animal remained submerged due, it is suggested, to lung vasoconstriction increasing the transfer factor. Blood in the dorsal aorta had a lower oxygen tension than that in the pulmonary vein. A right-to-left shunt occurred as blood moved through the heart. The degree of shunting increased as the animal remained submerged and pulmonary vasocon-striction occurred. Left-to-right shunt was relatively insignificant since oxygen tensions in the inferior vena cava and pulmonary artery were very similar. Carbon dioxide tensions were relatively constant during the breathing-diving cycle since Amphiuma removed almost all of this gas through the skin.
The Effects of Respiratory Acidosis in the Chick Embryo
Authors: Dawes C. M. , Simkiss K. 
Published: April 2021

ABSTRACT
Embryos of the domestic fowl have been incubated in normal conditions and in an atmosphere of 9 % carbon dioxide from day 9 onwards. There is a rapid increase in blood bicarbonate and base excess when the embryos are exposed to carbon dioxide. The increase amounts to about 14 m-equiv./l and is relatively constant from day 12 onwards. There is no detectable increase in titratable acidity or ammonium ion content of allantoic fluid which would indicate that the extra plasma bicarbonate ions were formed by renal activity. It is suggested that the extra bicarbonate of the blood is derived by resorption of eggshell minerals.