bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Technique of Free Skin Grafting in Mammals
Authors: Billingham R. E. , Medawar P. B. 
Published: April 2021

ABSTRACT
Methods are described for the execution of free skin grafts in rabbits, guinea-pigs and mice.
Much of the work in which use has been made of the techniques described above has been generously supported over a period of years by the Department of Plastic Surgery, University of Oxford (Prof. T. Pomfret Kilner, F.R.C.S.).
The Role of Radiation in Photodynamic Action
Authors: Calcutt G. 
Published: April 2021

ABSTRACT
It has been demonstrated that, within certain limits, the radiation of cultures of Paramecium bursaria, which had been kept in the dark, with wave-lengths greater than 3300 A., facilitates a subsequently elicited photodynamic response. A period of darkness following the pre-irradiation allows of a return to the normal condition. The role of radiation in the mechanism of photodynamic action is discussed.
The literature concerned with photodynamic action is surprisingly reticent upon the subject of the role played by the radiation used to induce the effect. It is tacitly assumed that the radiation, plays its part solely via the so-called ‘sensitizing’ agent. The possibility of direct action upon the test material appears to have been ignored. Recently (Calcutt, 1950), evidence has been put forward indicating that wavelengths greater than 3300 A. are effective in influencing the intracellular availability of sulphydryl groups. Additionally, it has been suggested that functional —SH groups are involved in the mechanism of photodynamic action (Calcutt, 1948). Further experimental work has been carried out to endeavour to elucidate this joint question of the role of radiation and —SH groups in photodynamic action.
The Swimbladder and the Vertical Movements of Teleostean Fishes
Authors: Jones F. R. Harden 
Published: April 2021

ABSTRACT
The vertical movements of a teleostean fish may be restricted by the presence of the swimbladder, which will increase or decrease in volume when the fish moves up or down in the water.
It is shown that the restriction that the swimbladder imposes to vertical movements involving a reduction in pressure will depend on physical factors such as
The resistance that the bladder and body wall offer to the expansion of the bladder gas. The percentage volume of the swimbladder and the density change of the fish when it is subjected to a reduction in pressure. The pressure reduction that leads to the rupture of the bladder wall.
A distinction is made between rapid and slow movements. In the former the compensatory ability of the fish must be considered and in the latter the speed with which the fish can accommodate itself to pressure changes.
An equation is derived from which the minimum speed at which a physoclist can migrate from deep to shallow water can be calculated. To solve the equation two factors must be determined experimentally.
Various experiments are described which were made on the perch, Perca fluviatilis, the wrasse, Crenilabrus melops the rockling, Onos mustela and the dragonet, Callio-nymus lyra. The results showed that there was a relation between the relative size of the swimbladder and the change in the density of a fish when it is subjected to a reduction in pressure; that the bladder and body wall of the perch offer little resistance to the expansion of the bladder gas ; and that the danger of the bladder wall rupturing might restrict the extent of rapid movements made by the perch.
Experiments on the restriction that the swimbladder imposes to the rapid and slow vertical movements of the perch will be described in.a following paper.
Studies on the Physiology of Ascaris Lumbricoides
Authors: Hobson A. D. , Stephenson W. , Beadle L. C. 
Published: April 2021

ABSTRACT
Vialli (1923, see Schopfer, 1927), Duval & Courtois (1928) and Schopfer (1924, 1925, 1926, 1927, 1932) have shown by means of freezing-point determinations that the osmotic pressure of the body fluid of Parascaris megalocephala and Ascaris vitulorum is lower than that of their hosts. Schopfer (1932) found that the depression of the freezing point of extracts of whole specimens of A. ovis and A. lumbricoides was in each case less than that of the intestinal fluid of the host. He (1932) also found a similar relationship in the case of Proleptus obtusus, an intestinal parasite of Scyliorhinus caniculus, and Panikkar & Sproston (1941) came to the same conclusion as the result of their work on an unidentified species of Angusticaecum from the tortoise. In free-living land or fresh-water nematodes the body fluid is presumably hypertonic to the environment, and Stephenson’s work (1942) indicates that in Rhabditis terrestris this is, in fact, the case, and that there is an active process of osmotic regulation by means of which this difference in osmotic pressure is maintained.
Studies on the Physiology of Ascaris Lumbricoides
Authors: Hobson A. D. , Stephenson W. , Eden A. 
Published: April 2021

ABSTRACT
For the investigation of many aspects of the physiology of Ascaris lumbricoidis and other parasitic nematodes the provision of a fluid medium in which they can be kept alive and healthy in the laboratory is necessary. This is a matter of considerable difficulty, since the natural environment of such animals contains organic substances which are subject to bacterial action. Consequently, most of the experimental work which has been carried out has been on animals kept in saline solutions to which organic constituents were not added. In view of the fact that balanced salt solutions are usually employed in physiological work, it is somewhat surprising to find that solutions of sodium chloride have been used by many recent workers (see, for example, Hamisch, 1933, 1935; Hoffmann, 1934; Waechter, 1934; Kriiger, 1936, etc.). Dewitz (1899), however, used sea water in the case of an unidentified nematode from the tissues of Scomber scombrus. Some later workers, such as Slater (1925), Adam (1932) and Hirsch & Bretschneider (1937), used Ringer or Tyrode’s solution for Ascaris lumbricoides and Toryu (1934) kept Parascaris equorum in Ringer. Davey (1938), working with adult Ostertagia circumcincta and Fenwick (1939) with larvae of Ascaris lumbricoides, developed, by means of a series of survival experiments, saline media in which the animals could be kept alive in the laboratory for some days. Baldwin (1943) also used a balanced salt solution in which adult A. lumbricoides would survive for as long as 10-11 days, although the worms were undoubtedly unhealthy after the first few days in this medium. Hobson, Stephenson & Beadle (1951 ; and see Hobson, 1948), working with A. lumbricoides, in 1941 used 29% and, later, 30% sea water as a medium. In this, individual specimens have survived in apparently healthy condition for as long as 28 days. Baldwin & Moyle (1947) have used a medium based upon Eden’s analyses (see later in the present paper) of the body fluid of the same species. In this the animals did not five longer than in Bald-win’s original medium (Baldwin, 1943), although they remained more active. The composition of the various media to which reference has been made is given in Table 1.
The Induction of Regeneration in the Hydroid Cordylophora Lacustris
Authors: Moore Janet 
Published: April 2021

ABSTRACT
Beadle & Booth’s work on grafting oral cones into reconstitution masses of Cordylophora lacustris has been repeated, confirmed and extended. Oral cone grafts induce the development from mass tissue of hydranth regions basal to the oral cone, and other regeneration of the mass is inhibited. Except in the most quickly developing material, induced development is significantly faster than ‘spontaneous’ development. Inducing action when grafted to a mass is not peculiar to the oral cone but is a property of all tissue with hydranth differentiation (the tentacular ring, subten-tacular region, hydranth neck and even pieces of tentacle), and of tissue containing the rudiment of hydranth differentiation (the tips of outgrowths developing from masses). Tissue which does not possess hydranth differentiation (unspecialized stem coenosarc and stolon tips) has no inducing activity but is absorbed into the mass without influencing its regeneration. Grafts of basal hydranth regions and outgrowth tips normally regenerate oral cones out of graft tissue, but induction may occur even when no oral cone is regenerated by the graft. Tentacle grafts do not regenerate an oral cone; the oral cone of the induced hydranth develops from mass tissue. Inducing power therefore does not depend upon the regeneration by the graft of an oral cone. Grafts of inverted oral cones or fragments of oral cones may produce induction. That inducing activity does not depend on the size, orientation or completeness of the grafted differentiated tissue further shows that it is the presence of hydranth differentiation in tissue, rather than any other factor, which confers inducing ability. No induction has been produced when an oral cone graft is separated from the host tissue by an agar or a cigarette paper barrier. Direct close contact between the graft and the host appears to be necessary for induction to be produced. Grafts of agar on to which oral cones have previously been squashed, macerated oral cones or killed oral cones do not produce induction. If macerated oral cone tissue becomes reorganized into a small fragment possessing the histological structure of part of an oral cone, induction may then occur. The separated constituents of differentiated tissue do not appear to be capable of producing induction.
A Comparative Study of the Lipids of the Vertebrate Central Nervous System
Authors: McColl J. D. , Rossiter R. J. 
Published: April 2021

ABSTRACT
The concentration of water, cerebroside (glycosphingoside), free and total cholesterol, total phospholipin, monoaminophospholipin (phosphoglyceride) and lecithin (phosphatidyl choline) was determined in the spinal cords of a series of vertebrates including representatives of the cartilaginous and bony fishes, amphibians, reptiles, birds and mammals. From these figures was calculatedthe concentration of ester cholesterol, sphingomyelin (phosphosphingoside) and kephalin. As was previously found for brain, the spinal cords of each of the species studied contained negligibly small concentrations of cholesterol ester. The concentration of each lipid in the spinal cord was very similar for different individuals of the same species, but for different species within the same class the mean concentration of many of the lipids extended over a wide range. The concentration of total cholesterol, sphingolipid and myelin lipid was greater in the spinal cords of mammals than in the spinal cords of the lower vertebrates. Expressed as a percentage of ‘essential lipid‘, the concentration of cerebroside, cholesterol, sphingomyelin, sphingolipid and myelin lipid, but not of lecithin and kephalin, was greater in the spinal cord than in the brain. For the spinal cords of the species studied, the mean concentration of cerebroside expressed as a percentage of ‘essential lipid’ was negatively correlated with the mean concentration of sphingomyelin. The results are discussed in relation to the chemical nature of the lipids of the myelin sheath of a vertebrate nerve fibre.
Observations on the Mechanism of Feeding in the Suctorian Podophrya
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
Podophrya sp., studied in this work, feeds on various holotrich ciliates. The tips of the tentacles adhere to the prey. Within a few minutes the cilia of the prey in the region where the Podophrya is attached stop beating. The stoppage spreads from here outwards over the surface of the prey. In some cases the surface of the Podophrya becomes wrinkled. The prey is broken down locally in the region of attachment, material from the prey flows up the tentacles into the Podophrya, and the Podophrya gets bigger, any wrinkles that may have formed becoming smoothed out in the process. Wrinkling of the Podophrya is shown by observations and experiments to be due to an expansion or growth of the body surface. This expansion serves to reduce the hydrostatic pressure within the Podophrya, so that feeding may proceed. It is suggested that expansion of the body surface, coupled with a supposed resistance to inward collapse, might provide suction for feeding. Wrinkling of the surface is ascribed to a local collapse which may be supposed to occur when uptake of food material from the prey fails to keep pace with the expansion.
Studies in Diurnal Rhythms
Authors: Cloudsley-Thompson J. L. 
Published: April 2021

ABSTRACT
A composite diurnal locomotory rhythm has been established in the woodlouse Oniscus asellus. This is correlated primarily with alternating light and darkness, and not with fluctuating temperature or humidity.
The intensity of the humidity response of the species is less in darkness than in light, and less still in darkness when the animals have been kept in darkness for some days previously. It increases with desiccation. The response to light is greater, too, in animals which have been kept in darkness for some days, and these tend to remain photo-negative in dry air whereas controls become photo-positive with desiccation. The sensitivity to carbon dioxide is much greater in animals from a culture kept in darkness than it is in controls.
The results obtained are discussed in relation to the nocturnal ecology of the species.
Sympathomimetic Activity in the Isolated Frog’s Heart (Rana Temporaria)
Authors: Smith C. L. 
Published: April 2021

ABSTRACT
In a previous paper (Smith, 1951) the occurrence of various types of relation between temperature and the pulse rate of the isolated frog’s heart was reported. Five main types of curve were observed and their chief features may be briefly summarized as follows. Type A showed an exponential relation between frequency and temperature, and corresponded to the ‘winter’ curve originally described by Barcroft & Izquierdo (1931). Type B was rather similar to A, but instead of the rates lying along an even curve they lay on two straight lines which intersected at about 10° C. Type C showed a linear relation between frequency and temperature over the range investigated and the value of the observed temperature coefficient (Q10) was about 2·5. This form corresponded to the ‘summer’ curve of Barcroft & Izquierdo (1931). Type D was of infrequent occurrence, and in this case the pulse rates for the upper and lower temperatures lay on straight lines of very similar slope, but which had different origins at 7° C. Type E again showed a linear relation between pulse rate and temperature, but in this case the observed temperature coefficient was significantly lower than that found for type C (2·1). It was further shown that pulse rate curves of type B or type D could be produced by treatment of type E hearts with an extract of anterior pituitary gland in the presence of added adrenaline. Type C curves were obtained from type E hearts when they were perfused with Ringer containing anterior pituitary extract, adrenaline and thyroxine. To explain these results it was suggested that there was a synergistic action between an anterior pituitary principle and adrenaline which was inhibited at temperatures below 10° C. Further, as types A, B and C pulse rate curves could be obtained from normal hearts in the absence of external adrenaline, the hypothesis was advanced that the isolated heart was under the influence of an active sympathomimetic substance even when it was being perfused with unmodified Ringer.
Optical Changes in the Membranes of the Sea-Urchin Egg at Fertilization, Mitosis and Cleavage
Authors: Mitchison J. M. , Swann M. M. 
Published: April 2021

ABSTRACT
Changes in birefringence and light scattering of the sea-urchin egg membranes at fertilization, mitosis and cleavage are described and illustrated. There is a close similarity between the changes in the cortex at fertilization and at cleavage. The changes in the cortex at cleavage start at the poles of the cell, and only later spread to the equator.
The Physiology of Contractile Vacuoles
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
The rate of output of the contractile vacuole of the suctorian Podophrya sp. was found to increase during feeding up to ten times. It decreased at the end of the meal but remained higher than it was before feeding. The extra output of the contractile vacuole during feeding was approximately equal to the decrease in volume of the prey minus the increase in volume of the Podophrya. In a typical meal roughly one-half of the food ingested by Podophrya was accommodated by expansion, and one half by concentration of the food taken in. This concentration was brought about by the action of the contractile vacuole.
The Effects of Posterior Pituitary Extracts on Water Balance in Bufo Carens and Xenopus Laevis, together with some General Considerations of Anuran Water Economy
Authors: Ewer R. F. 
Published: April 2021

ABSTRACT
The effects of pitressin and pitocin on water balance in Bufo carens and Xenopus laevis have been investigated. Bufo carens is most sensitive to pitressin, and shows an increased water uptake together with a well-marked anti-diuretic response. Xenopus reacts equally to the two extracts by an increase in water uptake, but there is no anti-diuresis. The effects of pitressin and pitocin in causing lymph accumulation and resorbtion of fluid from the bladder have been studied in Bufo regularis. Pitressin has the greater effect, and there are indications of seasonal variations in the magnitude of the response. The normal rates of water uptake of B. regularis, B. carens and Xenopus laevis have been measured. The two species of Bufo take up water rapidly, but Xenopus does so much more slowly. After desiccation the water uptake of Bufo regularis increases very considerably. This does not occur in Xenopus. There is a large weight increase after injection of posterior pituitary extracts in Bufo regularis and B. carens, but not in Xenopus laevis. The findings of other workers on the magnitude of the weight increase after posterior pituitary injections are summarized. The results are discussed in relation to the identity of the active principles of the anuran posterior pituitary and to the biological significance of the responses.
Flow Orientation as a Possible Explanation of ‘Wave-Motion’ and ‘Rheotaxis’ of Spermatozoa
Authors: Walton Arthur 
Published: April 2021

ABSTRACT
Flow orientation of spermatozoa in dense suspensions has been demonstrated by optical and electrical methods.
Relaxation time, i.e. the time required for a suspension of elongated cells, which have been orientated by flow, to regain a certain degree of random distribution when flow ceases, has been shown to be closely and inversely related to motility, as measured by impedance change frequency in the suspension.
Flow orientation may provide a physical explanation of ‘wave-motion’ and ‘rheotaxis’ of spermatozoa.
Wave-motion occurs in a suspension of elongate cells which possess progressive motility in the direction of the long axis of the cell. Orientation of the cells may be brought about by ‘short-range order’ or flow. Disorientation may be brought about by streams of orientated cells moving in random directions. In the suspension as a whole an equilibrium will be reached such that the forces tending towards orientation (short-range order or flow) are balanced by forces tending towards disorientation (streaming). In small regions, however, statistical variation in the direction and velocity of the streams set up by sperm movements will produce local disturbance of the equilibrium and turbulence or wave-motion will result.
Various Types of Ghosts Derived from Human Red Cells: Heat Fragmentation and Phase Optics Studies
Authors: Ponder Eric 
Published: April 2021

ABSTRACT
This investigation started with the incidental observation that a slight modification in the method used for preparing ghosts from human red cells results in a remarkable difference in one of the properties of the ghost; more specifically, when ghosts are prepared by the addition of large volumes of water, they are not fragmented by heat unless a certain concentration of salt is present (Ponder, 1951). Extension of these observations, made possible by phase-contrast optics, has led to the idea, already suggested by electron microscope studies, that a large number of kinds of ghost, each with its own characteristic properties, can be prepared from a single kind of red cell. This is a very different idea from the usual one that the ghost is a ‘residue’ which, apart from small differences in chemical composition, is essentially the same whether it is obtained from one kind of red cell or from another.
Parthenogenesis in the Mollusc Paludestrina Jenkinsi
Authors: Robson Guy C. 
Published: April 2021

ABSTRACT
The keeled form of Paludestrina jenkinsi is described and its distribution discussed. The keel is found to be non-heritable through three parthenogenetic generations. The evidence for the (a) environmental and (b) auto-genous origin of the keel is analysed. The result is a presumptive case in favour of the former, though such a keel is not among the structural modifications which have been proved, either by experiment or otherwise, to be produced by environmental factors. The various modifications of the keel show that, if of environmental origin, a more complex structural system is produced than is usual in such cases. It is suggested that, as the keel (or one of its derivatives) is found as a fixed character in another species of the same genus and in allied genera, it is deprived at present of the means of attaining genetic stability in P. jenkinsi.
The Properties of an Intercellular Matrix and Its Relation to Electrolytes
Authors: Gray J. 
Published: April 2021

ABSTRACT
The intercellular matrix of the cells on the gills of Mytilus edulis is readily dispersed by hydroxyl ions. All cations inhibit the action of hydroxyl ions, but the divalent metals are much more powerful than the monovalent metals. All divalent metallic ions except magnesium irreversibly coagulate the matrix at the hydroxyl ion concentration of seawater. This does not occur in the presence of magnesium ions. There is a marked difference between the action of different non-electrolytes, since in the absence of salts the matrix remains stable for a much longer period in sugar, or glycerine, than in urea. Alcohol in certain concentrations has a marked stabilising action in the absence of salts. With pure solutions of different monovalent sodium salts the anions can be arranged in a well-marked series in which the matrix is most readily dispersed in sodium iodide The relationship of the matrix to ions is similar to that between protein systems and ions, when attention is paid to both the electrostatic and lyophilic effect of the ions, and to the fact that the matrix is normally in equilibrium with a solution containing divalent metallic ions — magnesium in particular. The analogy must, however, not be pushed too far. The intercellular matrix of Mytilus cells can only possess a very slight electro-negative charge when in equilibrium with sea-water. If the constitution of the membrane is altered in such a way as to increase this charge, a type of matrix forms in which calcium is an essential constituent. Such a matrix appears to exist in echinoderms and in some other types.
The Spermatozoa of Sterile Bulls
Authors: Hancock J. L. 
Published: April 2021

ABSTRACT
Sterility in certain Friesian bulls is associated with a specific morphological abnormality affecting the acrosomes of their spermatozoa. This abnormality is visible in living spermatozoa and is also visible in fixed spermatozoa when precautions are taken to preserve the morphology of the cell. If such precautions are not taken, and the spermatozoa are subsequently stained by the nigtosin-eosin method, or with Heidenhain’s iron haematoxylin, or when such spermatozoa are examined with the phase-contrast microscope, the abnormality is inconspicuous. These difficulties do not arise when either the Giemsa stain or indian ink is used.