bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Function in the Locomotory System of the Dogfish Embryo. the Myogenic Stage of Movement
Authors: Harris J. E. , Whiting H. P. 
Published: April 2021

ABSTRACT
A brief description is given of some features in the special morphological organization of the neuromuscular system in the embryo of the lower vertebrates. The development of locomotory behaviour patterns in elasmobranchs is compared with that in other groups. The earliest movements of the embryo of Scyliorhimis caniculus have been photographically recorded ; the results of Wintrebert are confirmed. The movements persist unchanged after complete removal of the nervous system ; they are rhythmical and independent on the two sides. Any isolated portion of an actively contracting myotome band can act as its own pace-maker. The histological structure of the nerve cord and muscle at the time of these first movements is described in detail. There is strong evidence against any morphological link between the motor neurons and the myotome band; other neurons in the developing spinal reflex arc are similarly unconnected with one another. The results are discussed in relation to similar phenomena in other systems. Consideration is given to the mechanism of the excitation and transmission of the contractile process in the myotome band.
The Rate of Urine Production of Anodonta Cygnea
Authors: Potts W. T. W. 
Published: April 2021

ABSTRACT
The inulin clearance rate of a too g. Anodonta varies from about 0-2 ml./hr. at o° C. to 10 ml./hr. at 180 C. The rate of urine production, inferred from the initial rate of loss of weight in an isotonic solution, is 1-9 ± 11 ml./hr. at 15o C., and is thus of the same order as the inulin clearance rate.
Experiments on the Light Sense of the Hag, Myxine Glutinosa L
Authors: Steven D. M. 
Published: April 2021

ABSTRACT
The response of the hag to light consists of one or more local movements followed after a further interval by general locomotory activity. The first local movement has been used as a measure of the reaction time. The reaction time is inversely proportional to the intensity of the stimulus at illuminations less than about 10 e.f.c. At higher levels of illumination it attains a constant minimum value. Hags respond to intensities at least as low as 0·1 e.f.c. but only after several minutes illumination. Estimates of the penetration of light through sea water suggest that the hag’s light sense is of functional value. The spectral sensitivity maximum lies between 500 and 520 m μ. Hags are virtually insensitive to wave-lengths longer than about 600 m μ. The significance of the spectral sensitivity is discussed in relation to the spectral transmission of sea water and the evolution of photosensitive systems.
On The Reaction to Light of Myxine Glutinosa L
Authors: Newth D. R. , Ross D. M. 
Published: April 2021

ABSTRACT
That the effectively eyeless hag, Myxine glutinosa, is responsive to light was reported by Gustafson (1935). Our own interest was aroused by the behaviour of some hags (kindly sent to us by Dr Gustafson) which were being photographed. A tank containing a number of them was brightly illuminated for a few seconds only. Some 20 sec. later the animals, which had previously lain motionless in the semi-darkness, started, rather suddenly, to swim. The long delay between stimulus and response seemed to merit study while the definiteness of the response promised an important help to observation. The present paper reports the behaviour of hags under different conditions of illumination and a preliminary investigation of the sensory physiology of their responses.
The Excretion and Storage of Ammonia by the Aquatic Larva of Sialis Lutaria (Neuroptera)
Authors: Staddon B. W. 
Published: April 2021

ABSTRACT
A study has been made of the excretion and storage of ammonia by the aquatic larva of Sialis lutaria. About 90 % of the nitrogen excreted by the larva of Sialis during starvation was in the form of ammonia. The daily ammonia output averaged 10 μg. N/100 mg. wet weight. Ammonia was found to be excreted into the hindgut, presumably via the Malpighian tubules. The concentration of ammonia in the hindgut fluid averaged 136 mg. N/100 ml. Evidence was obtained that the tissue fluids are not maintained completely ammonia-free. Thus the total ammonia content of the body averaged 1·0 μg. N/100 mg. wet weight of tissue. The concentration of ammonia in the haemolymph averaged 0·50 mg. N/100 ml. Evidence was obtained that the larval tissues are capable of ‘storing’ appreciable quantities of ammonia. Thus ammonia did not accumulate in the tissue fluids of larvae prevented from excreting for a period of 5 days. Furthermore, it was found experimentally possible to raise the concentration of ammonia in the tissue fluids, the ammonia subsequently disappearing. The possible significance of this ‘storage’ mechanism was discussed. The method used for raising the concentration of ammonia in the tissue fluids, by immersing the larva for some time in a solution of dilute ammonia, was considered in some detail, particularly with respect to toxic effects. When the concentration of ammonia in the haemolymph had reached a level in the region of 7·0 mg. N/100 ml. toxic symptoms started to appear.
The Functions of the Ocelli of Calliphora (Diptera) and Locusta (Orthoptera)
Authors: Cornwell P. B. 
Published: April 2021

ABSTRACT
By determining the appropriate physical constants of the ocellus it is shown that in both Calliphora and Locusta the focal plane lies much deeper than the retinal space so that the eye cannot perceive form with any accuracy. The large visual fields afforded by their position on the head and the position and shape of their retinae suggest that the ocelli are efficient light-gathering units. The ocelli alone are unable to mediate phototactic responses to light of the intensities employed in these experiments. The efficiency of phototactic reactions mediated by the compound eyes is, under certain conditions, significantly greater when the ocelli are intact than when they are occluded. In Calliphora this stimulatory influence of the ocelli is not manifest at a low light intensity. In Locusta nymphs, ocellar occlusion produces an effect only when the compound eyes are light-adapted and orientation depends on light stimulating the anterior part of the eye. In both species, the experimentally observed behaviour is explicable on the theory that ocellar occlusion causes a decrease in the sensitivity to light of the anterior part of the compound eye.
Urine Production by the Antennal Glands of Palaemonetes Varians (Leach)
Authors: Parry Gwyneth 
Published: April 2021

ABSTRACT
Four methods for estimating the rate of urine flow in Palaemonetes varions are described. The rate is minimal when the external medium is approximately isotonic with the blood. All methods indicate that the rate increases progressively with increasing dilution of the external medium below 50 % sea water. There is some evidence to suggest that the rate increases in hypertonic external media. These results are discussed in relation to estimates of the urine production in some other Crustacea and in relation to the ecology of the genus Palaemonetes.
Inhibitors of Tyrosinase
Authors: Pryor M. G. M. 
Published: April 2021

ABSTRACT
It has been reported that if Drosophila larvae are ground to a fine paste with sand, the homogenate shows little tyrosinase activity, but that if the larvae are allowed to blacken in chloroform vapour before grinding, activity is increased. This has been interpreted as showing the effect of an intracellular inhibitor, set free by rupturing the cells, but destroyed by chloroform. This inhibitor has been identified by previous authors as a dehydrogenase. It is here suggested that the lack of activity of Drosophila extracts prepared with sand is due to destruction of tyrosinase as it oxidizes naturally occurring aromatic substrates. It is shown that tyrosinase is destroyed by oxidizing the aromatic substrate present in the cuticle of Calliphora larvae, or by very low concentrations of homocatechol. The aromatic substrate of Calliphora larvae is concentrated in the cuticle, and would be set free by fine grinding. Drosophila or Calliphora larvae yield a more active extract when ground with sand than when simply crushed, provided that they are tested soon after grinding. The tyrosinase activity of such extracts is not increased by chloroform or methanol. The compound between o-quinones and amino-acids is capable of oxidizing ascorbic acid or excess amino-acid without the aid of an enzyme, and of simultaneously reducing methylene blue. This reaction, rather than the activity of dehydrogenases, is probably responsible for most of the ability of damaged insect tissue to bleach methylene blue. The blood of insects normally contains dissolved oxygen in equilibrium with the air. The reaction involved in the blackening of insect blood may consume all the dissolved oxygen. Previous observations on fluctuations in the oxidation-reduction potential of the blood of Calliphora larvae with age are probably due to changes in the rate at which oxygen is consumed by the blood after it is shed. There does not therefore appear to be any valid evidence that tyrosinase is inhibited in vivo by the action of dehydrogenases. The absence of tyrosinase activity in undamaged tissue is probably due to the structure of the cytoplasm, which keeps enzyme and substrate apart. Instances of the inhibition of tyrosinase reported in Crustacea and Echino-dermata seem to be susceptible of the same explanation as in insects. The supposed inhibitory effect of sulphydryl groups reported for vertebrate melanophores is shown to be due to the combination of sulphydryl groups with o-quinones, which prevents the formation of melanins.
Membrane Potentials in the Muscles of the South American Frog, Leptodactylus Ocelatus
Authors: Harris E. J. , Martins-Ferreira H. 
Published: April 2021

ABSTRACT
The experiments described here were made in Brazil during 1953. Their primary purpose was to explore the properties of the muscle fibres of the locally available frog, Leptodactylus ocelatus, and to find out whether, in spite of the very different climate to which the animals are accustomed, their isolated muscles provide as convenient experimental preparations, and give similar results to those obtained, for instance, with the sartorius of European Rana temporaria. This was found to be the case, and in addition to repeating a number of established effects on Leptodactylus ocelatus, some new results obtained with changes in the ionic composition of the solution will be reported. Intracellular recording of resting and action potentials was used and the conditions were chosen so that the experiments could be compared with those made by other authors. In addition, an investigation of the effect of some of the variables upon the rate of extrusion of sodium from the muscle fibres was measured by radioactive tracer methods ; these results will be reported later.
The Movement of Sea-Urchin Spermatozoa
Authors: Gray J. 
Published: April 2021

ABSTRACT
Although the mechanical activity of spermatozoa plays an essential role in the process of fertilization there is little precise information concerning the type and speed of movement of individual cells in their normal state of activity. This paper represents an attempt to fill this gap with respect to a sea-urchin whose spermatozoa, being of the typical monoflagellate type, provide valuable material for the study of flagellar propulsion in general.
The Propulsion of Sea-Urchin Spermatozoa
Authors: Gray J. , Hancock G. J. 
Published: April 2021

ABSTRACT
The movement of any short length of the tail of a spermatozoon of Psammechinus miliaris and the characteristic changes which it undergoes during each cycle of its displacement through the water can be described in terms of the form and speed of propagation of the bending waves which travel along the tail (Gray, 1953, 1955); the form of the wave depends on the maximum extent of bending reached by each element and on the difference in phase between adjacent elements. The object of this paper is to consider the forces exerted on the tail as it moves relative to the surrounding medium and to relate the propulsive speed of the whole spermatozoon to the form and speed of propagation of the bending waves generated by the tail. The mathematical theory of the propulsive properties of thin undulating filaments has recently been considered by Taylor (1951, 1952) and by Hancock (1953); the present study utilizes and extends their findings but approaches the problem from a somewhat different angle. resistance, and consequently the transverse displacement (Vy) elicits reactions tangential and normal to the surface of the element. The latter force (δNy) has a component(δNysinθ) acting forward along the axis (xx ′) of propulsion; it is this component which counteracts the retarding effect of all the forces acting tangentially to the surface.
Electrometric Titration of Chloride in Small Volumes
Authors: Ramsay J. A. , Brown R. H. J. , Croghan P. C. 
Published: April 2021

ABSTRACT
The potentiometric end-point in the titration of chloride with silver nitrate depends upon the fact that the concentration of Cl- ions determines the potential of a silver wire coated with silver chloride which dips into the titration vessel. This chloride electrode is connected through a voltmeter with a reference electrode which completes the circuit, and when the end-point is reached there is a very rapid change of potential between the electrodes, of the order of 100 mV or more. This method is not only convenient but also promises to be practicable on the micro-scale where there is insufficient thickness of solution for the colour change of an indicator to be perceptible.
The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes
Authors: Kerkut G. A. , Taylor B. J. R. 
Published: April 2021

ABSTRACT
The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose or mannitol to a given concentration of Locke. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0-7 Locke to o-6 Locke, the change taking 43 min. This corresponds approximately to a change of 1 % of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.
Biochemical and Physiological Studies of the Purified Toxin of Walterinnesia Aegyptea ‘The Egyptian Black Snake’
Authors: Mohamed A. H. , Zaky O. 
Published: April 2021

ABSTRACT
Two methods for preparation of the toxin in a purified crystalline form are described. The toxin is probably a secondary proteose. It has an excitatory parasympathetic effect on the uterus of the guinea-pig and on the intestine of the rabbit. The effect is abolished by atropine. It causes excessive salivary secretion, again abolished by atropine. It causes partial or complete block of perfused isolated amphibian and mammalian hearts. It also causes extrasystoles. Both effects are abolished by atropine. The minimum lethal dose for rats is 0·035−0·05 mg. toxin/100 g. body weight. Atropine did not save the life of the animal although it prolonged it. The possibility of a histamine-like action of the venom is discussed.
The Role of the Symbiotic Bacteria in the Nutrition of Rhodnius Prolixus (Hemiptera)
Authors: Baines S. 
Published: April 2021

ABSTRACT
Earlier views of the nature of the association between Rhodnius and its symbiotic bacteria are confirmed. The bacterium is described as Nocardia rhodnii in accordance with more recent views of the classification of the Gram-positive filamentous bacteria. Experimental evidence is provided to show that the symbiotic bacterium is essential to Rhodnius because of its function in supplying certain B group vitamins, in which the normal blood diet of the host is deficient.
Sun Navigation of Apis Mellifica L. in the Southern Hemisphere
Authors: Kalmus H. 
Published: April 2021

ABSTRACT
The sun navigation of honey bees has been investigated in a region of the southern hemisphere where the sun was moving counter-clockwise during the observations.
Foragers from a strain long established in the region were fed in the evening on a dish in a particular geographical direction and transferred overnight to a new locality unknown to them. During the next day the majority of bees were at all hours searching in the direction of their previous training.
Foragers which were the offspring of queens recently imported in an inseminated state from the northern hemisphere showed after similar training systematically false orientation on the day of observation. The direction of their search shifted by about 30° per hour counter-clockwise from a direction about 90° clockwise from the training direction in the morning to the correct direction in the evening.
Bees of hybrid (local and imported) origin also showed false orientation.
The existence of innate mechanisms is postulated compensating in northern bees for the sun’s clockwise movements and in southern bees for the counterclockwise movement of the sun. The change in the direction of compensation must have occurred during the last 425 years, and a possible mode of this evolutionary process is discussed.
Factors Which Influence the Acquisition of Flagella by the Amoeba, Naegleria Gruberi
Authors: Willmer E. N. 
Published: April 2021

ABSTRACT
When placed in distilled water Naegleria gruberi changes from an amoeboid organism, with little evidence of polarity, to a highly polarized free-swimming flagellate. The details of this metamorphosis are described. The change is reversible. Alteration of osmotic pressure is not in itself the direct cause of the metamorphosis, though the loss of certain ions is clearly important. The metamorphosis is favoured by the presence of low concentrations (less than M/8O) of sodium bicarbonate, sodium lactate and sodium phosphate. The flagellate form probably occurs most frequently in conditions of neutrality ; but, in the presence of phosphate, acid conditions tend to be more favourable to the flagellate form, while in the presence of bicarbonate the optimum pH is nearer pH 8 0. The metamorphosis to the flagellate form is suppressed by a variety of agents including lithium salts, magnesium chloride and the sulphate ion under some conditions. These all act at concentrations which leave the amoeboid form in full activity. In some cases their action is decreased by the presence of bicarbonate in the medium.
Respiration in the African Swampworm Alma Emini Mich
Authors: Beadle L. C. 
Published: April 2021

ABSTRACT
Alma emini, a glossoscolecid oligochaet, is a common inhabitant of the waterlogged and often floating mat of decomposing vegetable matter which forms the substratum of the papyrus swamps of East Africa. Oxidation-reduction potential (E7) measurements in the field show that to within a fraction of a centimetre of the surface this material is strongly reducing and is presumably devoid of free oxygen. Alma lives with most of its body immersed in this material, but for much of the time it exposes to the air a tubular ‘lung ‘formed by the upfolding of the edges of the highly vascular dorsal surface at the hind-end. On retreating from the surface bubbles of air are often carried down enclosed in this tube. The dissociation curve of the haemoglobin is such as might well fit the animal to this mode of life. In the absence of CO2 it is saturated at about 2 mm. Hg of oxygen. A Bohr effect is not detectable unless the tension of CO2 is raised to about 200 mm. Hg, and even then it is slight. This would also fit it for respiration in a medium in which very high tensions of CO2 must occur.. In the laboratory it is unaffected by prolonged exposure to an atmosphere of pure CO2. Though apparently capable in the laboratory of a purely anaerobic metabolism, its behaviour in mud-water cultures suggests that it needs oxygen for survival in its normal environment. The possible functions of aerobic and anaerobic respiration are discussed.
Quick and Slow Contractions in the Isolated Sphincter of the Sea Anemone, Calliactis Parasitica
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
There are two kinds of neuromuscular activity in sea anemones that are full of interest for the comparative physiologist: (1) the conspicuous quick withdrawal movements which can be elicited by any strong stimulus; (2) the almost imperceptible and continuous slow changes of shape and position, incorporated in various feeding and pumping activities, which may be elicited by general or local stimulation of moderate intensity.
The Function of the Brain of Octopus in Tactile Discrimination
Authors: Wells M. J. , Wells J. 
Published: April 2021

ABSTRACT
The results of fifty-three experiments in which octopuses were trained to make tactile discriminations between the members of pairs of Perspex cylinders are reported. Grooves cut into these otherwise smooth cylinders varied in number and arrangement. The proportion of errors made in distinguishing such objects depends upon the difference between the proportions of groove on the objects concerned, and is not affected by the pattern or orientation of the grooves. It has thus been possible to measure the similarity to Octopus of the objects used and to predict the errors that will be made in any such discrimination.
When these results are considered in the light of the known nervous arrangements in the arms, it is possible to present a hypothesis about the mode of action of the peripheral tactile sensory system and the function of the brain. It is necessary to suppose that the latter distinguishes frequencies of nerve impulses in the sensory nerves from the arms; it is not necessary to postulate any projection of the sensory field or scanning mechanism involving the use of proprioceptive information.
Effect of Phosphate and Chloride Ions on Aerobic Metabolism of Bovine Spermatozoa
Authors: Salisbury G. W. , Nakabayashi N. T. 
Published: April 2021

ABSTRACT
Under the aerobic conditions of these experiments, dilution of bovine semen with phosphate ion depressed oxygen consumption and motility of sperm cells. However, fructose utilization and lactic acid accumulation were increased in the presence of phosphate ion. When semen was diluted with isotonic sodium chloride oxygen uptake was greater, motility was maintained better and fructose utilization and lactic acid accumulation were lower than in the phosphate-diluted semen.
Twice-washed cells in a diluent containing seminal plasma utilized more fructose and accumulated more lactic acid than those in plasma-free diluent. The depressive effect of phosphate on respiration was not due to H2O2 formation nor to changes of osmotic pressure.
The season of the year in which semen was collected influenced its metabolic response in each of the diluents studied. The presence of glucose-6-phosphate dehydrogenase activity was not conclusively demonstrated in cell-free extracts of bovine spermatozoa prepared by sonic oscillation.