bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the Nature of Immunity to Homologous Grafted Skin, With Special Reference to the Use of Pure Epidermal Grafts
Authors: Billingham R. E. , Sparrow Elizabeth M.
Published: April 2021

Homografts of pure epidermis, i.e. of skin freed from all dermal elements, survive their orthotopic transplantation between unrelated rabbits for 10-15 days. They elicit and succumb to a transplantation immunity reaction just as ordinary skin homografts do. The distinctive sequence of histological changes that take place in the dermis of a skin homograft during the course of its breakdown take place in the host’s own young fibrous tissue when this forms the bed underlying pure epidermal homografts. Although the breakdown of pure epidermal homografts is accelerated when they are transplanted to specifically immunized recipients, they normally survive for from 4-6 days. It is inferred that the serum and tissue exudates present in the bed to which such grafts are transplanted have no immediate inimical effect on the susceptible Malpighian cells when these are intimately exposed to them. The possible application of pure epidermal grafts, and more particularly of dissociated epidermal cells, has been investigated in attempts to demonstrate a specific toxic action against a donor’s cells of the blood, serum, and other derivatives of specifically immunized animals. After treatment in vitro, the ‘vitality’ of the epidermal grafts or cells was tested by transplanting them back to the animal from which they originated. It was found that epidermal melanocytes of guinea-pig’s skin are unaffected by prolonged treatment in vitro with ‘immune ‘blood and serum, with or without the addition of lymphocytes or spleen cells. The capacity of dissociated Malpighian cells in the rabbit to give rise to epithelium after grafting was completely or partially inhibited by treating them in vitro with excess immune serum for 22 hr. or longer at either 50 C. or 37° C. It is suggested that this effect indicates the presence of a protective iso-antibody in the serum of rabbits which have reacted against skin homografts. The probable role of this antibody in the breakdown of skin homografts in vivo is discussed.
Functions of the Omasum in the Stomach of the Sheep
Authors: Gray F. V. , Pilgrim A. F. , Weller R. A.
Published: April 2021

The processes which occur in the omasum of the ruminant have long been a subject of speculation and debate (Favilli, 1937). It was at first thought that the fluid portion of the digesta passed on from the reticulum was squeezed out in the omasum, and the larger food particles comminuted there, but no evidence has been offered which proves that either of these processes actually take place. As an alternative explanation of the characteristically high concentration of solids in the omasum it was later suggested that large amounts of water might be absorbed through the walls of the organ, and this suggestion has recently received strong support from the observation (Garton, 1951) that the concentrations of certain inorganic ions are often much higher in the omasal fluid than in the rumen fluid. Nevertheless, the possibility of permeation of the omasal wall by these ions makes them unreliable as accurate markers of the absorption of water; and the further possibility that some of the reticular contents may bypass the omasum and flow directly to the abomasum via the omasal groove has rendered equivocal the use of markers for the assessment of the extent to which water is absorbed. It has been suggested (Elsden, Hitchcock, Marshall & Phillipson, 1946) that the greater part of the fatty acids in solution in the liquid portion of the material received from the reticulum are absorbed from the omasum, but here again the evidence is incomplete because of lack of knowledge of how liquids and solids are passed through the omasum. Fatty acids are undoubtedly absorbed there (Barcroft, McAnally & Phillipson, 1944), and the ratio of acids to solids is much reduced (Elsden et al. 1946), yet if fluid were separated from the solids mechanically, rather than absorbed through the walls of the omasum, the absorption of fatty acid need not be as extensive as has been implied.
The Effects of High Hydrostatic Pressures on A Suctorian
Authors: Kitching J. A.
Published: April 2021

The suctorian Discophrya piriformis Guilcher has been subjected to pressures ranging from 1000 to 15,000 lb./sq.in. (68–1020 atm.). Pressures of 2000 lb./sq.in. and over cause a creasing of the body surface. Except at the higher pressures this occurs some seconds after the application of pressure. Creasing is accompanied by an expansion of the pellicle. At the lower pressures, there is also an expansion of the protoplasmic surface. A comparison may be made with the expansion of the body surface which occurs during feeding. In many cases, and particularly at the higher pressures, the protoplasm later separates from the expanded pellicle. With prolonged treatment it sometimes rounds up, and there is evidence of a loss of volume of the protoplasm. On release of pressure the protoplasm spreads back to the pellicle, usually within a few minutes. The wrinkled and expanded pellicle is then slowly reorganized to its normal shape and size, over a period of many hours.
The Physiology of Contractile Vacuoles
Authors: Kitching J. A.
Published: April 2021

A study has been made of the effects of sudden changes of temperature on the contractile vacuole of the suctorian Discophrya piriformis Guilcher. A sudden increase of temperature from below 15° C. by 5° or more causes a temporary fall in the rate of output, followed by a rise to a new level higher than the original. During the depression in activity the body swells slightly. The vacuolar frequency increases immediately but briefly when the temperature is raised, falls steeply when the depression sets in, and when secretion is re-established rises again to a level above the original. A sudden fall in temperature causes an immediate decrease in vacuolar frequency, followed by a partial restoration. The rate of output falls rather more slowly and remains low. In several cases a small decrease in body volume was observed. It is suggested that the contractile vacuole is really contractile. The observations on vacuolar frequency described in this paper are interpreted in terms of an inherent vacuolar rhythm which is modified by temperature and which is partially linked with rate of secretion.
Slow Contraction and Its Relation to Spontaneous Activity in the Sea-AnemoneMetridium Senile(L.)
Authors: Batham E. J. , Pantin C. F. A.
Published: April 2021

It has been known for some time that the most rapid reflex contractions of sea-anemones show a characteristic relation to the stimulus. Thus in Calliactis parasitica a short series of adequate electric shocks, given at a frequency of about 1 per sec., is regularly followed by a facilitated contraction of the marginal sphincter (Pantin, 1935a, b). That is, each successive shock sets up a nervous impulse which facilitates the response of the muscle to the next; so that the contraction increases by steps corresponding to the shocks. The facilitating effect of each impulse decays so that as the frequency of stimulation is lowered the response becomes smaller and finally vanishes.
The Activity of Slugs
Authors: Dainton Barbara H.
Published: April 2021

Slug activity is associated with conditions of high humidity, and this association has, not unnaturally, led to the hitherto untested assumption that it was in some way induced by the necessarily damp conditions. The experimental examination of this phenomenon, described in this paper, has shown that certain changes in temperature, and not conditions of high humidity, induce activity. Such temperature changes occur in the situations inhabited by slugs on just those occasions when slug activity is observed in the field.
The Oxygen Uptake of the Lobster (Homarus Vulgaris Edw.)
Authors: Thomas H. J.
Published: April 2021

In sea water the oxygen uptake of Homarus vulgaris is directly proportional to the oxygen concentration. The relationship applies over the temperature range 6-18° C. Within specified limits of size and condition, oxygen uptake is the same for both sexes. The relative oxygen uptake in sea water decreases as the weight of the animal increases. Oxygen uptake in sea water is effected mainly through the gills. The abdominal swimmerets, however, also serve in respiration and account for approximately 3 % of the total oxygen uptake. In sea water of constant oxygen tension, oxygen uptake increases with increasing temperature. Increase in oxygen uptake with temperature in sea water is mainly brought about by an increase in the gill ventilation rate. In addition, the degree of utilization increases. The relationship is a direct reflexion of the increased metabolic activity. The ventilation rate of gills is unaffected by a decrease of oxygen. The percentage of oxygen extracted by the gills increases as the oxygen concentration of the medium decreases. Under the influence of carbon dioxide respiratory movements become retarded at acidities greater than about pH 7·0 and are completely inhibited at around pH 6·5. At acidities less than pH 7·0 changes in the carbon dioxide concentration are without effect on the rate of the respiratory movements. The oxygen uptake in air, notwithstanding its low level, is directly proportional to temperature. The significance of the above results in relation to the respiratory functions of the blood is discussed.
The Mechanical Properties of the Cell Surface
Authors: Mitchison J. M. , Swann M. M.
Published: April 2021

A new instrument for measuring the mechanical properties of the cell surface is described. It consists of a micropipette connected to a moveable reservoir of water. The tip of the pipette is brought up to a cell and a bulge sucked out of the surface by lowering the reservoir. A plot of deformation (i.e. degree of bulging) against negative hydrostatic pressure gives a straight line for the sea-urchin egg at all stages. We have called the slope of this line the ‘stiffness ‘of the cell membrane ; it varies with the stage of the egg, the size of the pipette and the speed at which readings are taken. A comparison of the straight-line plots actually obtained with the curves to be expected from pure surface tension or from a thin-walled elastic sphere, leaves no doubt that the cell membrane is not behaving like either of these systems. It is concluded that the membrane is sufficiently thick to resist deformation by virtue of its own rigidity, resembling therefore a tennis ball rather than a rubber balloon or a fluid drop. An analysis of the problem in terms of a thick membrane is mathematically intractable, and is only possible by means of models. Experiments, using a large-scale pipette to suck bulges out of rubber balls, show that over a considerable range of wall thicknesses, the pressure-deformation curves are in fact linear. It is shown that the slope of the pressure-deformation curve or ‘stiffness’ depends on Young’s modulus and the internal pressure. It is not possible to separate these two variables by direct means. A dimensional analysis shows that it is permissible to scale down from model experiments to arrive at Young’s modulus and the internal pressure of the cell. For any given value of ‘stiffness’ there is a series of solutions, with values for the modulus decreasing from a certain figure, and values for the internal pressure increasing from nil. A limit can, however, be set to this series by other measurements.
The Mechanical Properties of the Cell Surface
Authors: Mitchison J. M. , Swann M. M.
Published: April 2021

Measurements were made with the cell elastimeter on the stiffness of the cell membrane in the unfertilized eggs of five species of sea urchin. Young’s modulus varies in the different species between the values of 0·91 × 104 and 2·08 × 104 dynes/c2. Experiments on the change of stiffness in hypo- and hypertonic media indicated that there is probably no internal pressure and no membrane tension in the normal egg. If, however, there is an internal pressure, measurements of the minimum shrinkage of the membrane necessary to produce wrinkling showed that this pressure cannot exceed 95 dynes/cm2. A drop in temperature of 18·5° C. produced an increase of stiffness by a factor of 2·1. These experiments, together with other evidence, suggest that for mechanical purposes the unfertilized sea-urchin egg can be compared to a hollow sphere filled with fluid and surrounded by a solid elastic wall (the membrane or cortex) about 1·5 μ thick and with an elastic modulus about 1·2 × 104 dynes/cm2. This degree of rigidity is sufficient to ensure the maintenance of shape of the egg without the presence of an internal pressure or a tension in the membrane. In everyday terms, the egg therefore resembles a tennis ball or a child’s rubber ball, rather than an inflated balloon or an oil drop in water.
Constituents of Bull Seminal Plasma
Authors: Rothschild Lord , Barnes H.
Published: April 2021

The concentrations of the main inorganic and certain organic constituents of bull seminal plasma have been examined. The average concentrations, in mg./100 ml., were: Sodium and potassium were found to be inversely correlated, r = −0.86 p<0-001. Calcium, chloride, fructose, citrate and total nitrogen were also strongly correlated (p<0-001), in such a way that a knowledge of the concentration of any one of the constituents enabled the average concentration of the other four in the sample to be predicted with considerable accuracy. Sodium, potassium and chloride were estimated by standard chemical methods and with the flame photometer (sodium and potassium) and by electrometric titration (chloride). The applicability of the alternative methods of estimation, which require very small quantities of seminal plasma, has been examined and is discussed. The freezing-point depression, Δ, of bull seminal plasma was-0-533, standard error of mean, 0-005. The A’s of a number of laboratory and field diluents were also examined ; with two exceptions they were found to vary markedly from A for bull seminal plasma.
The Structure of the Yolk of the Hen’s Egg, Investigated by Means of Its Permeability to 82Br
Authors: Maurice D. M. , Fidanza A.
Published: April 2021

82Br was mixed with the white of hen’s eggs maintained at I° C., and its concentration in the yolk and white measured after experimental periods ranging from 5 min. to 200 hr. In some cases the distribution of 82Br in the yolk was determined. From 5 hr. onwards the concentration in the yolk increased at a constant rate reaching on the average 2-5 % of that in the white after 200 hr. This suggested that the penetration was opposed by an external membrane of low permeability (7 × 10−5 cm./hr.). Before 5 hr. the amount of 82Br in the yolk was in excess of that predicted by this mechanism. This did not appear to result from contamination from the white and suggested that there was a layer of yolk external to the resistive external membrane and therefore this was not the vitelline membrane. Even after 100-200 hr. most of the 82Br which had penetrated remained in the superficial layers of the yolk. This showed that there was also a resistance to its penetration in the mass of the yolk itself. The bearing of this evidence on the structure of the yolk is discussed.
Some Tables for the Ionic Composition of Sea Water
Authors: Barnes H.
Published: April 2021

There exists a considerable and increasing interest in the ionic composition of the various tissues and body fluids of a wide variety of animals. During the course of such investigations a knowledge of the ionic composition of the natural environment from which the animals were taken is often required. Routine determinations of salinity are usually made in a Marine Biological Laboratory, but the concept of salinity (or chlorinity), of fundamental importance in oceanography, is somewhat artificial and confusion may be felt by those not familiar with the concept.
The Respiratory Currents in the Tracheal System of the Adult Honey-Bee
Authors: Bailey L.
Published: April 2021

The propodeal spiracles of the honey-bee remain closed in normal air but in air plus CO2 they open as the abdomen contracts, and close as the abdomen expands. The first thoracic spiracles remain open in normal air but in air plus CO2 they nearly close as the abdomen contracts, and open as the abdomen expands. When the bee is in normal air there is a strong tidal flow of air in and out of the first thoracic spiracles, but only a weak and variably directed stream of air through the body. It is deduced that when an active bee is producing metabolic CO2, directed streams of air enter the first thoracic spiracles and the abdominal spiracles and leave via the propodeal spiracles.
The Nerves and Muscles of Medusae
Authors: Horridge G. A.
Published: April 2021

It has been shown that a single large bipolar nerve cell in the subumbrella epithelium of Aurellia is necessary and sufficient to conduct the contraction wave across a narrow bridge from one part of the bell to another. This nerve impulse is accompanied by an electrical impulse of the kind usually recorded from the nerves of higher animals. These nerve cells are concerned only with the excitation leading to a contraction wave. There must be other pathways for other transmitted excitation.
The Energetics of Osmotic Regulation in Brackish- and Fresh-Water Animals
Authors: Potts W. T. W.
Published: April 2021

The dynamics of osmoregulation in an ideal semi-permeable animal are discussed. The theoretical minimum osmotic work is evaluated in terms of the surface area of the animal, its permeability and the concentrations of the blood, urine and external medium. It is shown that : (a) The most important means whereby a marine animal entering brackish water can reduce the strain upon its osmoregulatory mechanisms is by reducing the concentration of its blood. (b) In a brackish-water animal the production of urine hypotonic to. the blood has only a very small effect upon the osmotic work. (c) In a fresh-water animal the reduction of the urine concentration to the point at which it is isotonic with the medium can reduce the osmotic work by as much as 90 % ; but even a moderate reduction of the urine concentration, so that the urine is hypotonic to the blood but many times more concentrated than the medium, greatly reduces the osmotic work and is compatible with high osmoregulatory efficiency. These conclusions are discussed with reference to some fresh-water animals.
The Role of Peripheral Nervous System in Colour Changes of Bufo Arenarum Hensel
Authors: Stoppani A. O. M. , Pieroni P. F. , Murray A. J.
Published: April 2021

Stimulation of the peripheral nerves of Bufo arenarum Hensel produces a partial paling of the skin due to concentration of pigment in the intracutaneous melanophores, and dispersion of guanin-granules in the guanophores. This effect is attributed to the liberation in situ of an adrenergic-like substance. Noradrenalin and the cutaneous secretion (which contains adrenalin and active bases) play no part in the blanching of the skin. The nervous system plays a secondary role in the paling of the skin which follows hypophysectomy. There is no evidence that stimulation of the peripheral nervous system is essential for the colour changes of B. arenarum.
Electrophoretic Mobility of Red Cells and Their Ghosts as Observed with Improved Apparatus*
Authors: Ponder Eric , Ponder Ruth V.
Published: April 2021

This paper is concerned with the application of two new techniques, both of which depend essentially on improved instrumentation, to the study of the electrophoretic mobility of red cells and their ghosts. The first technique has been developed to overcome difficulties which are encountered in the measurement of the mobility of ghosts. If the ghosts are substantially haemoglobinized, they can be seen, although with some difficulty, with the ordinary microscope and their mobility can be measured in an electrophoresis cell such as that described by Abramson (1934); if they are relatively Hb-free, on the other hand, they are almost invisible under the ordinary microscope, and can be seen satisfactorily only with phase contrast. The great majority of existing measurements of the mobility of ghosts, accordingly, are measurements of the mobility of ghosts which contain relatively large amounts of Hb. The new vertical cell to be described uses phase-contrast optics, and is fitted with removable electrodes which have several advantages over those usually employed. The second technique is the result of the observation that the Antweiler electrophoresis apparatus with a Philpot-Svensson attachment, although designed for the separation and observation of the mobilities of protein fractions, can also be used for measuring the relative mobilities of red cells and their ghosts.
An Investigation of the ‘Chronometer’ Factor in Bird Navigation
Authors: Matthews G. V. T.
Published: April 2021

An investigation was made of that part of the sun navigation hypothesis which proposes that birds detect longitude displacement by comparing home time (provided by an internal ‘chronometer’) with local time (estimated from the highest point of the sun arc). Shearwaters were exposed for 4 days, and pigeons for ten days, to an artificial day 3 hr. in advance of normal. This did not result in any confusion of their orientation when released to the east. More drastic treatment was then used, pigeons being subjected to 4–5 days of irregular light/dark sequences, followed by 5–11 days of regular sequences, advanced or retarded with respect to normal. In tests from the west (2), east and north after this treatment, the ‘chronometers ‘had apparently been affected and the birds showed a definite tendency to fly in the predicted false direction—east after an advanced day, west after a retarded one. Variations in the time-in-sight, and in the proportion of the more rapid returns supported the conclusions drawn from the orientation data. In a minority (25 %) of the birds, the evidence suggests that the ‘chronometers ‘were not affected. It is concluded that these new results, taken with those produced previously, strongly support the suggestion that a form of complete, bico-ordinate sun navigation is used by birds.
The Cuticular Waterproofing Mechanism of the Worker Honey-Bee
Authors: Glynne Jones G. D.
Published: April 2021

It is now widely accepted, following the work of Alexander, Kitchener and Briscoe (1944 a–c), Wigglesworth (1944, 1945) and Beament (1945), that the thin layer of lipoid material which is present on or near the outer surface of insect cuticle serves to restrict the evaporation of water from the animal. Existing knowledge of the nature of this waterproofing layer has been built up from observations on the effect of dusts, heat, detergents and organic solvents on the rate of evaporation from intact cuticle and also from a study of the changes in permeability of natural and artificial membranes when coated with thin layers of lipoid material.
The Transpiration of Terrestrial Isopods
Authors: Bursell E.
Published: April 2021

The transpiration of three species of Isopoda has been investigated ; Armadillidium shows the highest resistance to desiccation, Oniscus the least, and Porcellio is intermediate. The permeability of isopod cuticle is limited by lipoids which impregnate the endocuticle. If the temperature is raised above the lipoid melting-point a marked increase in permeability results. Isopods show a characteristic decline in transpiration rate during exposure to desiccating atmospheres. The high initial rate of evaporation is due mainly to loss of water from layers of the cuticle external to the lipoid barrier. There is a progressive decrease in the permeability of the integument during desiccation. This is brought about by a shrinkage of the cuticle, which leads to a closer packing of lipoid molecules. The mechanism of this structural alteration is based on an interaction between endocuticular proteins and the ionic constituents of body fluids; in the course of desiccation the blood concentration increases and there is a corresponding decrease in the dispersion of endocuticular elements.
The Function of the Lyriform Organs of Arachnids
Authors: Pringle J. W. S.
Published: April 2021

Experiments involving the recording of impulses in sensory nerves in the appendages of a scorpion and an amblypygid show that the slit sensilla (lyriform organs) of these arachnids are mechanoreceptors, sensitive to strains in the cuticle and analogous to the campaniform sensilla of insects.
The Permeability and Structure of the Cuticle of the Aquatic Larva of Sialis Lutaria
Authors: Shaw J.
Published: April 2021

The permeability to water of the cuticle of Sialis larvae has been measured, using heavy water as tracer. The penetration was slow, the permeability constant being only 1·8 × 10−2 cm./hr. at 20°C. There was no obvious difference between the rate of water influx and outflux. The rate at which water penetrated into the tissues from the blood was much greater than through the cuticle. The Q10 for diffusion through the body surface was high, lying between 3·0 and 3·8. The osmotic uptake of water was calculated to be about 1 % of the body weight per day at 10°C. Drinking of water did not occur in normal larvae, but in larvae with the blood volume reduced, osmotic uptake of water through the gut did take place and the gut wall was much more permeable to water than the cuticle. A similar intake of water probably occurred during moulting. The permeability of the cuticle to chloride was measured and also found to be of a low order (P= 1·04 × 10−4 cm./hr. at 17°C.). Sodium diffused out of the larva at the same rate as the chloride. Histological examination of the cuticle showed that in the abdomen it was thin and consisted of a 7 µ. thick endocuticle and a 1 µ epicuticle. Over the thorax it was thicker, and a polyphenol layer was present as the outer layer of the epicuticle. There was indirect evidence of the presence of a wax layer. Wax was extracted from the cuticle, and the thickness of the layer from which it was derived was estimated by means of a monolayer technique. In the cuticle of the abdomen and gills the thickness averaged 0·1 µ. The permeability to water of the cuticle was compared with that of terrestrial insects and was found to be much greater. This difference was not due to the thick ness of the wax layer but probably to some physical properties of the wax. The cuticle of Sialis larvae showed no ‘critical temperature’ or sudden change in the permeability properties with temperature over the range of temperatures studied.
Ionic Regulation in the Muscle Fibres of Carcinus Maenas
Authors: Shaw J.
Published: April 2021

Measurements have been made of the concentrations of potassium, chloride, calcium and magnesium, the conductivity and the membrane potential of single isolated fibres of the carpopodite extensor and flexor muscles of Carcinus maenas. Analyses of whole muscles gave the total concentration of the cations as 224 mM./kg. H2O, of which potassium accounted for 120 mM./kg. and sodium 54 mM./kg. Of the anion fraction chloride only accounted for 54 mM./kg. H2O. The analyses of the separated fibres were the same as for the whole muscle. The average specific resistance of the fibres is 56 Ω-cm. This represents a concentration of muscle ions of about 200 m.equiv./kg. and the electrolyte content of the muscle is not much more than a third of that of the blood. Between 72 and 91 % of the total muscle fibre cations are present in an ionized form. The average membrane potential is 58 mV. The ratios of the concentrations of potassium ions and chloride ions in the blood and muscle fibres suggest that these ions may be passively distributed across the membrane. The low concentration of sodium ions in the fibre probably indicates the operation of a ‘sodium pump’ as has been proposed for vertebrate muscles. The distribution of calcium and magnesium cannot be explained in simple terms. The correspondence between the equilibrium potentials for potassium and chloride ions and the membrane potential suggests that theory of ion distribution put forward by Boyle & Conway for frog’s sartorius muscle may also be applicable to Carcinus muscles.
Functioning of the Insect Ocellar Nerve
Authors: Hoyle G.
Published: April 2021

The median ocellar nerve preparation of the locust Locusta migratoria has been re-investigated. The nerve contains six nerve fibres of which the two largest are 8 μ in diameter. The nerve fibres transmit propagated nerve impulses when the ocellus is illuminated or darkened. This disposes of the claim (Parry, 1947) that the ocellar nerve exerts an effect on the brain as the result of electrotonic spread from a depolarized region in the ocellus. The retinal potentials consist of a reduction of potential at the back of the ocellus on illumination and vice versa on darkening. This is the converse of the situation implicit in Parry’s exposition. Three kinds of nervous response are obtained from the ocellar nerve: an ‘on’-discharge, an ‘off’-discharge and a continuous dark-discharge. Corresponding discharges of nerve impulses are obtained from the circumoesophageal commissure. The ocellus must function principally as an indicator of changes in light intensity.
Osmoregulation and Ionic Regulation in Hydra
Authors: Lilly Sylvia J.
Published: April 2021

Isolated tentacles of Hydra viridis were placed in solutions of sucrose of different known concentrations. In concentrations of sucrose greater than 0·04 M the tentacles shrank, and it was found that the ectoderm, endoderm, and enteron all contributed to this shrinkage. Both ectoderm and endoderm are highly permeable to water. Calculations suggest that the ectoderm cells are at least as permeable as various other cells which have been investigated by many workers. Shrinkage of the tentacle was very slight in 0·05 M sucrose, and no shrinkage occurred in 0·04 M sucrose. It is therefore suggested that the internal osmotic pressure is equivalent to that of 0·04−0·05 M sucrose. The uptake of the radioactive ions 24Na, 82Br, and 42K by Pelmatohydra oligactis has been investigated. All these ions are concentrated above the levels in the external medium. The relations between internal and external concentrations have been determined for sodium and bromide. The internal sodium concentration is maintained at a steady level with external concentrations varying from 5·4 m.moles/1. to approximately 0·20 m.mole/1. The internal bromide level has been shown to fall as the external bromide decreases from 2·5 to 0·05 m.mole/1. Higher external bromide concentrations could not be used as the animals were not healthy in solutions containing more than 0·25 g./l. NH4Br. The internal bromide is also shown to be depressed by the addition of chloride to the external solution. The results obtained indicate that the cells of Hydra are highly permeable to water, and also capable of maintaining an internal concentration of certain ions well above that of the external medium. This requires some form of regulation of water content and of ionic content. In the case of the latter it is not at present possible to say whether it is an active uptake of cations or anions.
The Breakdown of the Thoracic Gland in the Adult Insect, Rhodnius Prolixus
Authors: Wigglesworth V. B.
Published: April 2021

The thoracic or ‘prothoracic’ glands of insects, which are the source of the growth and moulting hormone of the larval and pupal stages, degenerate and disappear soon after the final moult. In the adult Rhodnius the large nuclei of these glands are at an advanced stage of disintegration within 24 hr. of moulting, and at 48 hr. they have completely disappeared (Wigglesworth, 1952). The object of the present work was to study the physiological control of this breakdown.*
Comparative Studies of the Thyroid Function in Teleosts of Tropical and Temperate Habitats
Authors: Fortune P. Y.
Published: April 2021

The presence of thyroid gland tissue in teleosts was first reported by Simon (1844), and later its structure was shown to consist of follicular units similar to those in the thyroid gland of higher vertebrates. The teleostean gland is not discrete but consists of numerous scattered follicles.
The Sources of Energy for Flight in Mosquitoes
Authors: Clements A. N.
Published: April 2021

Reserve deposits of fat and glycogen are known to serve as sources of energy for flight in various insects. Among the Diptera only glycogen has been shown to serve this purpose ; the respiratory quotient of Drosophila in flight is close to 1·0 (Chadwick, 1947), and during flight glycogen disappears from the fat body but the deposits of fat are untouched (Wigglesworth, 1949). Tabanus has also been shown to use fat body glycogen during flight while apparently making no use of the fat deposits (Hocking, 1953).
The Wetting of Insect Cuticles by Water
Authors: Holdgate M. W.
Published: April 2021

The water contact angles of insects show a wide range of variation, which is broadly correlated with surface roughness and with habitat. The contact angles of species inhabiting stored products or carrion are greatly modified by contamination. This produces large variations between apparently similar individuals. In terrestrial insects surface roughness increases the contact angles to very large apparent values. Detailed analyses of its effect have been made in the pupa of Tenebrio molitor and the adult Calliphora erythrocephala. In some aquatic insects surface roughness leads to a reduction in the contact angles; this has been studied in the nymph of Anax imperator. Prolonged immersion in water causes a lowering of the contact angles of all the insects examined, and the low angles of many aquatic species may therefore be the direct effect of their environment. In some aquatic species there is evidence of the active maintenance of a large contact angle during life. Changes in contact angle accompany processes of cuticle secretion and will occur at any moult if changes in roughness or habitat take place. The observed variations of surface properties can be explained without assuming any variation in the chemical composition of the cuticle surface. Wetting properties are of little value as indicators of cuticle surface composition. The biological aspects of insect surface properties are briefly discussed.
The Nerves and Muscles of Medusae
Authors: Horridge G. A.
Published: April 2021

Evidence is presented to show the shortening of the refractory period of some of the elements in a population of coelenterate muscle fibres following frequent stimulation of the bell of Rhizostoma pulmo.
The Nerves and Muscles of Medusae
Authors: Horridge G. A.
Published: April 2021

The co-ordination of the swimming movement (beat) and feeding response in Aequorea forskalea has been studied with particular attention to the pathways taken by the excitation. The rapid through-conducting system which co-ordinates the beat is sharply distinguished physiologically from the radial system which co-ordinates feeding. The spontaneous origin of the beat and its rapid marginal conduction are both inhibited while the radial muscle is contracting. Inhibition of this type has been observed in other genera of Hydromedusae
Ionic Regulation in the Muscle Fibres ofCarcinus Maenas
Authors: Shaw J.
Published: April 2021

The electrolyte composition of the carpopodite extensor and flexor muscles of the chelae of Carcinus maenas living in diluted sea waters has been studied. The increase in water content of the muscles of crabs from 20% sea water corresponds to a maximum degree of swelling of 25 % of the initial weight. The resting membrane potential remains constant at 59 mV. over the whole range of blood concentrations studied. Chloride is lost from the fibres and its concentration in the muscle is always about one-tenth of that in the blood. Sodium ions are actively secreted from the muscles, and a steady state is reached when the concentration in the muscle is also about one-tenth that in the blood. The sodium and chloride concentrations in the muscle are approximately the same. The potassium concentration of the muscle falls as the blood is diluted, but the ratio of muscle potassium to blood potassium increases from 10 to about 20. Potassium appears to be actively retained in the muscle. The fall in concentration of muscle calcium and magnesium can be explained in terms of the swelling of the fibres alone and the fibre membrane is probably not permeable to these substances. The fibre is also probably impermeable to the larger part of the anion fraction. It is only sodium and potassium ions which are actively regulated and the result of these processes is that the muscle sodium balances the muscle chloride and the muscle potassium balances the impermeable anion fraction. It is suggested that on the extent to which the muscle cell can withstand blood dilution depends the degree to which it can resist swelling.
Further Studies of Gas-Filling in the Insect Tracheal System
Authors: Buck John , Keister Margaret
Published: April 2021

In Sciara larvae exposed to total anoxia before moulting, all visible movement and all visible change in the content of the tracheal system cease. Moulting and tracheal gas-filing can be postponed at least hr. beyond normal time. In most third-stage larvae exposed to 0·3-0·75 % O2 before the third moult, the future fourth-stage tracheal system, which is present fully-formed in the body, fills with gas. This shows that although moulting invariably precedes gas-filling under normal circumstances it need not do so. In premoult larvae which have filled their trachea with gas upon exposure to 0·3-0·75 % O2, the tracheae fill again with liquid when the larvae are put back into atmospheric air. This reversal of gas-filling can be alternated with gas-filling several times in the same individual. The fact that in reversal of gas-filling an increase in pO2 promotes liquidfilling, whereas in moulted larvae it not only never leads to liquid-filling but actually accelerates gas-filling, indicates that some basic, but at least temporarily reversible physiological or chemical change occurs in the tracheae or in the metabolism of the peritracheal tissue, near the time of moulting. A partial explanation of the observed phenomena can be made in terms of a combination of active uptake and physical uptake of tracheal liquid. Evidence for the existence of both types of mechanism, separately, has been adduced by Wigglesworth in other material.
Seasonal Variations in the Growth Rate, Thyroid Gland Activity and Food Reserves of Brown Trout (Salmo Trutta Linn.)
Authors: Swift D. R.
Published: April 2021

Seasonal variations in the growth rate, food reserves and activity of the thyroid gland of hatchery-reared brown trout have been investigated. Two peaks of maximum growth rate were found, in spring and autumn. A marked depression of rate occurred during midsummer and winter. Fat which was laid down along the mesenteries and pyloric caecae was found to be the main food reserve. Glycogen was found in small quantities in the liver and muscle. The composition of the muscle and liver was constant except for an autumnal fall in the female liver glycogen level. The fat reserves reached a peak of 23 % by weight of the gut wall during July then fell to 5 % in autumn. Maturation of the gonads commenced in females in June and in males in July and was completed during October. The protein content of the ovary increased by 16%, and of the testis by 10%.The fat content of the ovary increased by 3 %. A new method is described for the determination of thyroid activity in fish using radioactive iodine. Peak thyroid activity was found to occur in midsummer.
The Water Relations of Earthworms
Authors: Roots Betty I.
Published: April 2021

Suitable media have been found for maintaining the activity of the nephridiostome cilia of two earthworm species for about 24 hr. at 18° C. or below. The nephridiostome cilia of Lumbricus terrestris are less resistant to hypotonic media, and more resistant to hypertonic media, than those of Allolobophora chlorotica. When the medium is suddenly diluted, the nephridiostome cilia of L. terrestris and A. chlorotica have a period of hyperactivity and/or increased amplitude of the beat followed by a return to normal activity. The temporary effect after a change to a hypertonic medium takes the form of decreased activity or inhibition. In hypotonic solutions, vesicles are formed on the marginal cells and later disappear provided the dilution has not been too great. A change in the osmotic concentration of the medium is responsible for the vesicles and the temporary effects on the cilia, whereas the inorganic ion concentration is responsible for the long-term effects. There is no axial gradient affecting the activity of the nephridiostome cilia in relation to the osmotic concentration of the medium. No differences were detected between garden and Lake Windermere specimens of A. chlorotica.
Facilitation in Sea Anemones. IV. The Quick Response of Calliactis Parasitica at High Temperatures
Authors: Ross D. M.
Published: April 2021

Preceding papers of this series have dealt with the effects of a number of treatments on the quick responses of the sea anemones Calliactis parasitica and Metridium senile. Pantin’s (1935) analysis of the quick closing response in these animals showed that it is not normally elicited by single electrical stimuli, nor by stimuli following each other at intervals greater than about 3 sec. To get the closing response electrical stimuli must be given within a definite frequency range, at intervals of from about O-2-2-5 sec. at room temperatures. Between these limits, the closer the stimuli the bigger the response, with responses occurring, of course, only to the second and subsequent stimuli. This remarkable example of a facilitated response in which the response can only occur when facilitation has been set up, and in which the amount of facilitation determines the size of the response, raised many interesting problems. My work has centred on the approach of trying to set up experimental conditions in which single stimuli are effective, as this seemed a promising way of finding out more about the nature of this kind of facilitation.
The Eyes and the Photonegative Behaviour of Nephtys (Annelida, Polychaeta)
Authors: Clark R. B.
Published: April 2021

The photoreceptors found in the Nephtyidae are: (a) Two pairs of vacuolated cells lying in pigment cups, with accessory cells, embedded in the posterior part of the supra-oesophageal ganglion.(b) One or two cells, which may or may not be vacuolated, on either side, lying a little anterior to the ganglion.(c) Undifferentiated epidermal cells surrounded by pigment granules may be photosensitive. There are both morphological and behavioural grounds for concluding that the prostomial eyes of Nephtys are homologous with the eyes of Nereis, and that they are involved in the same types of behaviour. The frequency with which Nephtys swims is, within limits, a linear function of the light intensity. Although the ganglionic eyes are directional receptors the worm does not orientate itself in a light beam; presumably the light reaching them is too diffuse. In the very small species N. cornuta, the eyes are close to the surface of the brain and the worm does orientate itself in a light beam. Swimming is an essential prelude to burrowing, and the brighter the light the more frequently the worm swims and the sooner it is buried. Activity in light can be inhibited by stimulating receptors on the dorsal surface of the animal by contact.
The Mechanical Properties of the Cell Surface
Authors: Mitchison J. M.
Published: April 2021

Measurements were made with the cell elastimeter on the effect of a number of reagents and of changes in pH on the rigidity of the cell membrane of unfertilized sea-urchin eggs. The membrane rigidity was increased by dithiopropanol, thio-glycollate, chloracetophenone, a polyethanoxide and zinc ions. It was lowered by trypsin, cetyltrimethyl ammonium bromide and sodium dodecyl sulphate. Most of the other reagents, including respiratory inhibitors and calcium ions, had no effect. The membrane has a minimum rigidity at a pH of about 5-7.
Cellulose Digestion by the Silverfish Ctenolepisma Lineata*
Authors: Lasker Reuben , Giese Arthur C.
Published: April 2021

It is the prevailing opinion to-day that the majority of species of animals which feed upon plants or plant products are unable to hydrolyse cellulose in spite of its abundance (Baldwin, 1952), depending instead upon the sugars, starches, fats and proteins present in the plant tissues. This implies the lack of a suitable alimentary enzyme, cellulase, or symbiotic gut micro-organisms which could perform that function. Study of cellulose digestion in animals is hampered by the difficulty of defining the role of the micro-organisms of the gut. If cellulolytic action is found in extract of tissues or in secretions of glands, the question remains whether or not this activity is attributable to micro-organisms; conversely, finding a cellulose-digesting microbe in the intestine of an animal does not prove conclusively its benefit to the animal.
Storage and Utilization of Reserves by the Garden Chafer, Phyllopertha Horticola L
Authors: Laughlin Roger
Published: April 2021

Samples of all stages of Phyllopertha hortícola L. have been analysed for fat, total nitrogen and glycogen. Total nitrogen increases throughout the larval feeding period, while fat and glycogen are laid down mainly in the latter half. From November, when the third-instar larva goes into hibernation, until June, when the eggs have been matured and laid, no food is taken. Of the store of fat and glycogen in the hibernating larva at the beginning of the winter, half is used up by the time the adult emerges. The other half is used in the formation of eggs. Adult feeding provides energy for the post-oviposition activity period.
The Relationship of Oxygen Consumption to Age and Weight During the Post-Embryonic Growth of Locusta Migratoria L
Authors: Clarke Kenneth U.
Published: April 2021

The weight and oxygen consumption of individual locusts, six from each instar, have been measured at 12-hourly intervals throughout each stadium.

An analysis of short duration changes shows that fluctuations in live weight are unavoidable in the growing animal, and that they are accompanied by fluctuations in oxygen consumption. In time the latter lag behind the former.

As the fluctuations of these two variables are out of phase, there is a considerable range of oxygen consumption which must be regarded as normal for any given weight. Calculations are made to find the limits of these fluctuations compatible with normal growth.

The changes that occur during a stadium can be represented by a straight trend line for both weight and oxygen consumption. Exceptions occur in the case of weight of the adult where two straight lines are necessary, one for the growing phase and one for the steady phase of this instar. In certain cases in the fifth instar two straight lines are necessary to express the trend in oxygen consumption which may show an abrupt change in the middle of the stadium.

A high degree of correlation is found between the trend lines for weight and oxygen consumption in the early instars. A low degree is found in latter instars where the weight increases and the oxygen consumption remains nearly constant.

A curve representing the changes of weight and oxygen consumption that occur during the growth of the locust has been constructed.