bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sensory and Motor Interaction in the Locomotor Reflexes of Crabs
Authors: Evoy W. H. , Cohen M. J. 
Published: April 2021

ABSTRACT
Proprioceptive reflexes involved in control of the mero-carpopodite (MC) joint in walking legs of Cancer magister are mediated by four groups of sensory cells: two cell groups (myochordotonal organs), located proximally in the leg segment, which are associated with a receptor muscle and come under efferent control, and two cell groups (MC organs) located distally which signal joint position and movement but are independent of efferent control. Resistance reflexes, which oppose passive movements of the joint, are evoked by both types of proprioceptive organs. Reflexes evoked by the MC organs are maximally effective at the extremes of joint position. Reciprocal inhibition of antagonistic muscle groups appears to occur entirely at synapses within the central nervous system. Efferent control of the receptor muscle comes under the influence of both the myochordotonal and MC organs. The reflexes evoked by the MC organs on the receptor muscles are similar to those which impinge on the main flexor. The myochordotonal organ excites the receptor muscle on joint movements away from the rest position. Interaction of input from the two types of sense organs provides the system with a dynamically determined reference point for the basic postural position. This may be altered by efferent control of the receptor muscle. Reflexes evoked by both types of proprioceptive organ spread to the other walking legs, but are more labile than reflexes to the same leg.
An Investigation of the Electrogenic Sodium Pump in Snail Neurones, Using the Constant-Field Theory
Authors: Moreton R. B. 
Published: April 2021

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.