bluuebunny/crossref_metadata_2025 huggingface dataset:
An Investigation of the Electrogenic Sodium Pump in Snail Neurones, Using the Constant-Field Theory
Authors: Moreton R. B.
Published: April 2021

Sodium ions injected into giant neurones of Helix aspersa by diffusion from low-resistance microelectrodes caused hyperpolarization of the cells. Under these conditions the behaviour of the resting potential could be described by a modified ‘constant-field’ equation, including a term representing the effect of a potassiumsensitive, electrogenic sodium pump. Exposure to potassium-free solution, ouabain or cyanide abolished the hyperpolarization, and caused a gradual fall in the intracellular potassium concentration, as estimated from the constant-field equation. Assuming that this fall was due to replacement of intracellular potassium by injected sodium ions, it was possible to calculate the rates of injection and pumping of sodium ions, and, using the measured membrane resistance of the cell, the hyperpolarization which the sodium pump could cause, if it were electrogenic. This was related to the observed hyperpolarization, supporting the view that the latter was caused by stimulation of the electrogenic sodium pump.
An Acridid Auditory Interneurone
Authors: Rowell C. H. Fraser , McKAY J. M.
Published: April 2021

The alpha neurone habituates to repetitive short (40 msec.) or long (2–3 sec.) pulses of sound. The response decrement to 10 short pulses at 1/sec. is exponential. Twenty-five minutes is required for complete recovery to 20 short pulses at 1/sec. No dishabituation followed various changes in stimulus repetition. The C.N.S. affects both response level and habituation. In 13% of all animals the neurone was completely inhibited by the head ganglia and was disinhibited by decapitation. Progressive lesions reveal strong inhibition by the head ganglia, and possibly weaker inhibition by the abdominal chain; the prothoracic ganglion has no apparent effect. Removal of the head ganglia almost halves the habituation rate; further removal of the abdominal chain may give a further slight reduction; the prothoracic ganglion has no effect. There is a significant negative correlation between response level and habituation. This could be partially explained if the absolute response decrement is independent of response level. The remaining decrease in habituation observed suggests either a further link between response level and habituation at the synapse, or possibly independent central control of both. Central control affects habituation more than response level. Spontaneous variation in response level is unaffected by the various central lesions. It thus arises in the posterior thoracic ganglia, and not as descending inhibition or excitation from higher centres. These findings are related to the animal’s biology and to previous work.
A Technique for Discriminating Direction of Propagation of Action Potentials Recorded From an Intact Mixed Nerve
Authors: Rowell C. H. Fraser
Published: April 2021

Activity is recorded in the nerve by two external electrodes spaced a known distance apart. Action potentials trigger 10 μsec. pulses in each channel. Those of one channel generate, after a variable delay, selector pulses which gate the output from the other channel, and this is applied to an electronic counter or other display. As action potentials conduct at finite velocity, gate and delay times can be set to accept and count only impulses of a given range of conduction velocities propagating from the selector electrode to the counter electrode. Reversal of input connexions allows discrimination of impulse traffic moving in the reverse direction. This is best done from a magnetic tape recording of the same activity; the recorder for this purpose must meet stringent requirements. Simultaneous signals at both electrodes are rejected, distinguishing between action potentials and other potential changes, and thus allows retrieval of low amplitude nervous activity from recorded noise. Other applications include selection of impulses of a given amplitude or conduction velocity, and the measurement of conduction velocities of a population of different nerve impulses.
The Physiology of the Antennal Gland of Carcinus Maenas (L.)
Authors: Binns R.
Published: April 2021

Amino acids are actively reabsorbed by the antennal gland of Carcinus in all concentrations of sea water, but there is never complete recovery of these molecules from the urine; even in animals in 100% sea water amino acids are eliminated in the urine. The urine concentration of amino acids is related to (i) the blood amino acid concentration and (ii) the rate of urine production. An increase in either or both of these factors, for example, when animals are in dilute sea water, raises the U/B ratio of amino acids. The rate of reabsorption of amino acids increases as the amino acid load on the antennal gland is raised. When reabsorption is maximal, the rate of transport is about seven times greater than at normal concentrations of amino acids in blood and urine when the animal is in 100% sea water. Increases in blood amino acid concentrations when crabs are placed directly into dilute sea water are taken to be the result of changes in free amino acids of muscle which occur under these conditions. This intracellular regulation in dilute media is initiated when the blood sodium concentration is approximately 400 mM/1.
Secretion by the Malpighian Tubules of Rhodnius. The Movements of Ions and Water
Authors: Maddrell S. H. P.
Published: April 2021

The Malpighian tubules of Rhodnius will secrete at a normal rate in solutions containing no potassium ions and the rate is unaffected by changes in the potassium concentration, when the balance of cationic concentration is made up by sodium ions. In the absence of sodium ions the rate of secretion is much reduced. The addition of very small amounts of sodium-containing solution brings about an abrupt recovery in the rate and thereafter the rate is unaffected by further increases in the sodium concentration. In solutions containing either sodium or potassium with choline making up the balance of monovalent cations, the rate of fluid secretion depends linearly on the concentration of either sodium or potassium. The tubules will concentrate either sodium or potassium when they are present at low concentration in the bathing fluid, even in the face of a very much larger concentration of the other cation. This suggests that there are separate mechanisms for the handling of these two ions. Secretion can be supported by a solution containing ammonium ions in place of sodium and potassium. The tubules behave, at least in the short term, as if they were unable to distinguish ammonium from potassium. Chloride ions appear to play a special role in that only bromide ions and, to a limited extent, nitrate ions will substitute for them. The rate of secretion depends linearly on the chloride concentration. The tubules secrete a fluid which is practically iso-osmotic to the bathing fluid. The rate of secretion depends inversely on the osmolarity of the bathing fluid. The rate of movement of solute is little affected by these changes of osmolarity. It appears that water movements follow, and are closely linked with, solute movements. Copper, cyanide, iodoacetate and azide ions and 2,4-dinitrophenol all stop secretion when added to the bathing medium. Ouabain, acetazolamide and mammalian ADH all have no effect on the rate of secretion and ouabain has no effect on the composition of the secreted fluid. 5-Hydroxytryptamine (serotonin) will stimulate a rapid flow of secretion. Apparent neurosecretory axons have been found which supply the tubules. They do not contain enough diuretic activity to do more than play a minor role in diuresis. They may contribute to the rapid onset of diuresis or may affect the Malpighian tubules in some other way. The evidence suggests that the tubules function by secreting chloride, potassium and sodium ions into the lumen (it is speculated that this may conceivably involve the active transport of all three ions) and that water movements closely follow these ion movements so that a rapid flow of iso-osmotic fluid is achieved.
Permeability to Water of the Shell of the Egg of Locusta Migratoria Migratorioides, with Observations on the Egg of Teleogryllus Commodus
Authors: Browning T. O.
Published: April 2021

Eggs of Locusta migratoria migratorioides were cut open at one end, the tissues were removed, and the empty egg shells were filled with water or with an osmotic solution. The open end was tied off to form a balloon. Balloons containing water were placed in osmotic solutions, and those containing a solution were immersed in water. Balloons were made from eggs 1 or 2 days old before water absorption had begun, from eggs during the course of rapid water absorption and from eggs in which water absorption was complete. Diapausing and non-diapausing eggs were used. The hydropylar end of the egg was included in the balloons in half the observations. All balloons containing solution gained water and all those containing water lost it. Shells from diapausing eggs were much less permeable than all other categories. Little difference was observed between balloons whether the hydropylar end was present or not. Eggs exposed to unsaturated air lost water rapidly, except those in diapause. Balloons made with the shells of young eggs of Teleogryllus commodus were also permeable to water in both directions. The results are discussed in the light of their contribution to an understanding of the control of the absorption of water in insect eggs.
The Relative Efficiency of Gaseous Exchange Across the Lungs and Gills of an African Lungfish Protopterus Aethiopicus
Authors: McMahon B. R.
Published: April 2021

Of the three genera of lungfishes living today Neoceratodus, the Australian lungfish, is possibly the most primitive. The respiratory physiology of this animal has been extensively studied in recent years (Grigg, 1965a, b, c; Lenfant, Johansen & Grigg, 1966; Johansen & Lenfant, 1967) and the conclusions these authors draw support the assumptions of the earlier workers in this field (Dean, 1906; Longman, 1928; Spencer, 1891), who maintained that in this animal the lung was an accessory respiratory organ used principally when the animal was in poorly aerated water. The gas exchange occurring over the gills is apparently sufficient to satisfy the requirements of the animal in well-aerated water. Earlier workers on the respiratory physiology of Lepidosiren, the South American lungfish, suggested that in this animal the lungs were the principal respiratory organs (Carter & Beadle, 1930; Cunningham, 1934; Kerr, 1897, 1898). Sawaya (1946) found that the gills accounted for only 2% of the total oxygen uptake, and Johansen & Lenfant (1967) confirmed that the lungs were the principal site for oxygen exchange but thought that some carbon dioxide might be exchanged via the aquatic route. These conclusions show that these two forms are well adapted to their predominant habitat. Neoceratodus is usually found in permanent, well-aerated waters, which only rarely become stagnant (Grigg, 1965 c) and is only a facultative airbreathing form. Lepidosiren, on the other hand, is normally found in marshy waters which are not only often extremely hypoxic and hypercarbic, but are also liable to dry out periodically. Lepidosiren is an obligatory air-breathing animal and can survive the periods of drought by aestivating in a burrow in the mud (Kerr, 1898).
Optic and Static Contributions to Ocular Counter-Rotation in Carp
Authors: Traill A. B. , Mark R. F.
Published: April 2021

This paper describes a method for measuring static eye reflexes in restrained but unanaesthetized fish. Ocular counter-rotation in response to movement round the transverse axis of the body was studied in detail by means of denervation experiments and changes in the direction of incident light. Both body position, measured by the labyrinths and light direction, measured by the eyes, contribute to counter-rotation. Round about the normal attitude of the fish ocular counter-rotation is proportional to the angular deviation of the body from horizontal. The gain of the system measured this way can change according to the excitability of the fish but the proportional relationship is retained.
Locomotion of the Limpet, Patella Vulgata L
Authors: Jones H. D. , Trueman E. R.
Published: April 2021

The locomotion of Patella has been studied by histological, photographic and experimental techniques. The foot consists principally of dorso-ventral and transverse muscles and has no longitudinal muscle fibres near to its sole. The pedal haemocoel is limited to a region of small spherical cavities, extending for 0 ·5 mm. above the sole, two pedal sinuses and several lateral vertical channels. Patella moves forward by means of retrograde alternate ditaxic pedal locomotory waves, but during rarely observed backward movement the waves are direct. During tight turns the limpet uses forward locomotion on one half of the foot and backward locomotion on the other. During the passage of a retrograde locomotory wave the foot is lifted off the substrate by about 0 ·2 mm. and the pressure beneath the sole falls by about 6 cm. of water. A model is proposed to account for locomotion utilizing the dorso-ventral muscles as the sole propulsive agents in the hydraulic system of the foot. This system consists principally of the dorso-ventral and transverse muscles, the spherical cavities of the pedal haemocoel and the fluid enclosed beneath each locomotory wave. Both fluid systems may be utilized during contraction and relaxation of different groups of dorso-ventral muscles.
Impulse Patterns in the Flight Motor Neurones of Bombus Californicus and Oncopeltus Fasciatus*
Authors: Mulloney Brian
Published: April 2021

Each of the motor neurones innervating the indirect flight muscles of Bombus and Oncopeltus fire regularly during flight, not in patterned bursts. The several motor neurones innervating one muscle fire at about the same rate and have a weak tendency to fire synchronously, but all possible relative timings occur in each flight. Neurones innervating different muscles have no preferred relative timing, and may have different frequencies. The motor patterns of Bombus and Oncopeltus are very similar. These patterns could be generated by a model including common excitatory input to each of the neurones innervating one muscle and by weak electrotonic short-latency synaptic coupling between the motor neurones. Different sets of neurones would receive different excitatory input, and antagonistic sets seem to be coupled by a weak inhibitory mechanism. Recruitment of motor units was observed in Bombus during low-frequency activity. Synergistic units in Bombus fire in near-perfect synchrony during periods when the bee is warming up but not flying. When the bee begins to fly, there is a sudden shift to the output pattern characteristic of flight. The patterns of impulses in these insects have characteristics shared by both dipteran patterns and by orthopteran and lepidopteran patterns. The flight systems of Orthoptera, Lepidoptera, Hemiptera, Hymenoptera and Diptera also have many anatomical similarities. The anatomical similarities and the several common characteristics of the motor output patterns in these orders support the hypothesis that there was one primordial flight mechanism common to the origin of these orders, from which the different mechanisms which exist today have evolved.
Respiration in An Air-Breathing Fish, the Climbing Perch, Anabas Testudineus
Authors: Hughes G. M. , Singh B. N.
Published: April 2021

A study has been made of the patterns of respiration in climbing perch (Anabas testudineus) living in water containing different concentrations of oxygen and carbon dioxide and also in air-exposed fish. The fish breathes both water and air in normal tap water. The intervals between air-breaths are irregular and vary within the range 8–15 min. Air-breathing increases in water of high CO2 content. The time interval between air breaths falls with increasing CO2 content. Gill ventilatory frequency increases when 5–10% CO2 is bubbled into the water. Aquatic respiration stops and only aerial respiration occurs if more than 20% CO2 is bubbled into the water. Three factors, CO2 content, pH and O2 content of water, control the respiratory patterns in climbing perch. Of these CO2 content appears to be most important for fish living in water. The climbing perch can live for long periods (6–12 h during observations made) in water of very high CO2 content (20–33vols. %). In such hypercarbic water gases are only exchanged through the air-breathing organs. The mouth and opercula are closed tightly and gill ventilation stops completely. Exposure to air increases air-breathing but the frequencies are irregular. Inhalation of hypoxic gas or pure nitrogen also evokes air-breathing.
Aerodynamics of Gliding Flight of A Black Vulture Coragyps Atratus
Authors: Parrott G. Christian
Published: April 2021

A black vulture (mass = 179 kg) gliding freely in a wind tunnel adjusted its wing span and wing area as its air speed and glide angle changed from 9·9 to 16·8 m/s and from 4·8° to 7·9°, respectively. The minimum sinking speed was 1·09 m/s at an air speed of 11·3 m/s. The maximum ratio of lift to drag forces was 11·6 at an air speed of 13·9 m/s. Parasite drag coefficients for the vulture are similar to those for conventional airfoils and do not support the contention that black vultures have unusually low values of parasite drag.
Cardiac Ganglion of Limulus: Intracellular Activity in the Unipolar Cells
Authors: Palese Vincent J. , Becker Jane L. , Pax Ralph A.
Published: April 2021

The electrical activity of unipolar cells of the cardiac ganglion of Limulus has been examined with microelectrodes to determine the electrical properties and the functional relationship between unipolar cells. Resting membrane potential in these cell averages −43 mV. Correlated with each contraction of the heart there occurs a burst of activity which consists of a sustained depolarization of several seconds on which is superimposed a series of small 2–5 mV spikes. Activity which occurs during the initial phase appears to be the result of presynaptic inputs to these cells. Spike activity during the recovery phase is probably endogenous to the cell from which we are recording. The specific membrane resistance for the soma membrane averages 12 700 Ω. cm2. The time constant has a value of 19·6 ms. The specific membrane capacitance measures 1·54 μF/cm2. External stimulation produces a number of different responses in the unipolar cells which are dependent upon a number of factors. These responses can be classified into at least three types: (a) a driven response similar to a spontaneous burst; (b) slowly rising potentials which may be antidromic spikes.
The Regulation of Calcium and Magnesium in the Brackish Water Polychaete Nereis Diversicolor O.F.M
Authors: Fletcher C. R.
Published: April 2021

Nereis diversicolor tolerates changes in the concentration of calcium and magnesium in its coelomic fluid proportional to the concentrations in the medium between chlorosities of 100–1000 mM/kg of water. In lower salinities both ions are maintained relatively constant providing that the ratios of these ions to chloride in the medium are similar to the ratios in sea water. The ratio of the concentration of calcium in the coelomic fluid to the concentration in the medium is a function of the salinity of the medium but not of the calcium concentration. Both calcium and magnesium are at lower electrochemical potentials in the coelomic fluid than in the medium, indicating that it is not necessary to invoke active uptake. The rate of calcium influx is substantial. In salinities below 10 mM of chloride/kg of water the urine must contain less calcium than the coelomic fluid. The significance of these results is discussed.
Bending Moments in Free-Swimming Flagella*
Authors: Brokaw C. J.
Published: April 2021

Starting with the simple hydrodynamic assumptions of earlier work on flagellar movement, an exact analysis of the bending moments in a flagellum moving through a viscous solution has been developed. The results illustrate the variation in the resistance to bending and unbending resulting from viscous forces as a function of time as bends move along a flagellum. These bending moments are o at free ends of the flagellum, and rise to peak values of 2–3 times their average value near the middle of the flagellum, for movement patterns similar to those normally found on sea-urchin spermatozoa. The approximate expressions for bending moments and energy expenditures developed in earlier work are reasonable estimates of the average values of these quantities. Bending and unbending points propagate at reasonably constant velocities in the distal portion of free-swimming flagella, in spite of the large variations in the resisting moment resulting from viscous forces. The propagation velocity of individual bending and unbending points, or an individual bent region, is therefore probably not controlled by the resistance to bending and unbending at these points. Some mechanism for internal coordination of the activity of different regions of the flagellum appears to be required. In flagella, as in cilia, the external work done against viscous resistances is not uniformly distributed along the length of the flagellum. These conclusions provide additional support for ‘sliding filament’ models of flagellar bending.
The Dimensions and Sensitivities of Semicircular Canals
Authors: Ten Kate J. H. , Van Barneveld H. H. , Kuiper J. W.
Published: April 2021

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

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

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

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

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

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

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

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+> Co2+ > 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

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

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

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

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

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

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.
Gas Exchange With Air and Water in an Air-Breathing Catfish, Saccobranchus (≡Heteropneustes) Fossilis
Authors: Hughes G. M. , Singh B. N.
Published: April 2021

Gas exchange of Saccobranchus fossilis with water and air has been studied under various experimental conditions which were designed to simulate some of the conditions of tropical Asia. In tap water the fish exchanges gases with both water and air. When kept in air-saturated water it can exchange gases with water alone for periods of 6–12 h or even more. In de-oxygenated water, with free access to air, it obtains oxygen from the air and can five for several days under these conditions. In air-saturated water more oxygen is obtained from water (60 %) than from air (40 %), but in hypoxic water this ratio is reversed. When the fish is submerged in water, free access to air being prevented, the oxygen consumption is reduced, even in air-saturated water. In hypoxic and hypercarbic water oxygen consumption is further reduced. In air-saturated water about 17% of the oxygen enters via the skin and the rest via the gills. When exchanging gases with water alone and subjected to a gradual hypoxia, the fish shows a less dependent respirator. When the fish is removed from the water its oxygen consumption is reduced. A greater reduction occurs when the fish is kept in de-oxygenated water but allowed to breathe air. When the fish is exchanging gases with both water and air very little carbon dioxide is released into the air (RQ = 0·17). The total RQ in fish removed from the water is low, i.e. 0·58. The fish can survive in hypercarbic water only, provided that the content of carbon dioxide does not exceed 14·5 volumes %, when surfacing becomes necessary.
Connective Tissue Mechanics ofMetridium Senile: II. Visco-Elastic Properties and Macromolecular Model
Authors: Gosline John M.
Published: April 2021

The visco-elastic properties of the body-wall connective tissue (mesogloea) of the sea anemone Metridium senile were previously studied by Alexander (1962). He carried out creep tests (extension under constant stress) over long periods of time and observed that the tissue could be extended reversibly to over three times its initial length with very small forces. The material behaved very nearly like a single Voigt element with a retardation time of about 3500 sec. Although Alexander did not propose any specific molecular mechanism to account for the extensibility and apparent slow elasticity, he did note that collagen is thought to be a major component of mesogloea and suggested that the collagen must play a major role in determining the mechanical properties of the tissue.