bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Efferent Regulation of the Muscle Spindle in the Frog
Authors: Katz Bernhard 
Published: April 2021

ABSTRACT
Matthews’s experiments (1931a, b) have established that the muscle spindle of the frog contains a sense organ which responds to stretch and ceases to respond when the surrounding muscle fibres shorten. In addition, the spindle is known to possess a motor supply of its own, a bundle of small striated ‘intrafusal’ muscle fibres. These fibres run through the spindle capsule (Barker, 1948 ; Katz, 1949, fig. 1) where they establish intimate contact with the sensory nerve, while being separated by a lymphatic space from the ‘extrafusal’ tissue. These muscle fibres are said to lose their striations at the region of contact with the sensory terminals. The anatomical arrangement suggests that the intrafusal muscle bundle pulls directly on the stretch receptor, in contrast with the ordinary muscle fibres which will release the tension on the sense organ if they shorten. A contraction of the intrafusal muscle fibres, therefore, must affect the response of the stretch receptor in a manner very different from that of the surrounding mass of ‘extrafusal’ fibres. The function of the intrafusal muscle fibres is believed to be a regulation of mechanical ‘bias’ on the sense organ, but little is known concerning their motor innervation and the physiological conditions under which they are thrown into activity.
The Structure of the Insect Egg-Shell in Relation to the Respiration of the Embryo
Authors: Tuft P. H. 
Published: April 2021

ABSTRACT
Many insect eggs are able to avoid mechanical injury and desiccation because they are protected by an egg-shell or chorion which is tough, rigid and relatively waterproof. These properties tend to make it impermeable to gases, and since the egg contains a living embryo, there must be provision for the diffusion of an adequate volume of oxygen into the egg. The way in which this is achieved has never been satisfactorily explained. Specialized respiratory structures have been described in many species of insect egg, especially in those of parasites (Maple, 1937), and a respiratory function has sometimes been ascribed to the system of micropylar canals that penetrate the shell in hard-shell eggs, but until now there has been no direct evidence for the respiratory function of these structures. Indeed it seems unlikely, at first sight, that sufficient oxygen could diffuse through such small areas of the shell to satisfy the needs of the embryo, although in some species there can be little doubt that oxygen uptake is restricted to a small part of the shell; in certain species of capsid, for instance, the eggs are embedded in the tissues of a plant with only the caps exposed to the air.
Rectilinear Locomotion in a Snake (Boa Occidentalis)
Authors: Lissmann H. W. 
Published: April 2021

ABSTRACT
The mechanics of three common modes of locomotion in snakes has been subjected to a detailed analysis (Gray, 1946; Gray & Lissmann, 1950). These three modes are (i) the serpentine or horizontal undulatory movement; (ii) the concertina movement; (iii) the crotaline or side-winding movement. A fourth, less common mode, described as ‘rectilinear movement’, has aroused considerable interest since Home (1812) published his ‘Observations intended to show that the progressive motion of snakes is partly performed by means of ribs’.
Seasonal Changes in Blood Sugar, Fat Body, Liver Glycogen, and Gonads in the Common Frog, Rana Temporaria
Authors: Smith C. L. 
Published: April 2021

ABSTRACT
Seasonal changes in the weights of fat body, gonads and liver, liver-glycogen content, and blood sugar have been followed by observations on monthly samples of Rana temporaria which had been kept in captivity for 3 days without food. Three periods during which the blood sugar was high (from 54 to 62 mg./ 100 ml. of blood) were observed during the year: at the spawning season in March, in June and July, and in November. The hyperglycaemia of June and July was accompanied by the rapid development of the fat body. This phase was succeeded by that of gonad regeneration, during which there was no further storage of fat or liver glycogen, and the blood sugar was low (about 40 mg./ioo ml. of blood). When gonad regeneration was nearing completion glycogen storage in the liver became the dominant feature, and the blood sugar tended to rise again. A sex difference in blood sugar was observed at certain periods. From June to September the female blood sugar was higher than that of the male, but from September to January the relationship was reversed. This may be correlated with the differing rates of gonad regeneration in the two sexes. During the winter months, when the food intake was reduced, the frogs utilized some of their stored fat and glycogen and the blood sugar was low (about 40 mg./ioo ml.). The hyperglycaemia found at the spawning season was accompanied by the rapid depletion of the fat and glycogen stores. In April and May, after the breeding season, when the frogs were feeding actively, the blood sugar was low and apparently neither fat nor glycogen was being accumulated. It is suggested that this was a period of tissue repair and possibly of growth.
The Mechanics of the Blood Vascular System of Ascidiella Aspersa
Authors: Haywood C. A. , Moon H. P. 
Published: April 2021

ABSTRACT
The reversal of the tunicate heart involves two problems: first, why it stops beating in a particular direction; and secondly, why having stopped it should then reverse. Two types of theory have been put forward, one based on the idea that a ‘back pressure’ is gradually built up which compels the heart to stop, and the other depending on opposing centres of contraction at each end of the heart taking control alternately. The present paper provides quantitative evidence, based on Ascidiella aspersa (O. F. Mueller), that a back pressure is built up. The faster the heart beats the more frequently reversals occur, a back pressure building up more rapidly when the heart beats quickly. Various criticisms of the back-pressure theory are considered and discussed. Examples are given of other closed contractile systems containing fluid which show reversal, the tunicate heart being by no means unique.
Muscular and Hydrostatic Action in the Sea-AnemoneMetridium Senile(L.)
Authors: Batham E. J. , Pantin C. F. A. 
Published: April 2021

ABSTRACTThe majority of sea-anemones present to the eye an almost constant shape which only changes as the result of activities of a very simple kind. This is true, for instance, of Calliactis parasitica, the subject of an earlier study (Pantin, 1935). The unstimulated animal rarely departs from the form of a short cylinder surmounted by a disk bearing the tentacles round its edge and the mouth at its centre. In contrast with Calliactis, Metridium senile is notable for the variety of shapes which it assumes (Pl. 7). It may be fully expanded with a narrow or with a wide column (e, f). The same anemone may next day be found contracted down to a mere button-like object (d). It may indulge in a variety of contortions in which it is laterally bent, or possesses deep transverse constrictions locally or completely embracing the column (g, i). The whole anemone may on occasion temporarily assume a shrivelled and contracted condition (h), in which it might easily be discarded from the aquarium as dying ; but which, in fact, is a normal temporary state from which there is comparatively rapid recovery (i, f). At other times, particularly during locomotion, a part of the body may become greatly distended (c). Prolonged observation of Calliactis shows that even here there is some variation of shape, though less evident than with Metridium.
Some Properties of the Photoreceptors of the Brook Lamprey
Authors: Steven D. M. 
Published: April 2021

ABSTRACT
This paper describes an investigation of the physiological characteristics of the light receptors situated in the skin of the ammocoete larva of the brook lamprey, Lampetra planeri (Bloch). The interest of these organs lies in the fact that they are the only type of simple photoreceptor among the Vertebrates of which we possess any precise information. They may well be considered a kind of functional link between the simpler types of photoreceptor systems, which are found in many Invertebrates, in Pholas, Mya and Ciona, for example, and the fully developed image-forming eye of Vertebrates. We are at present almost completely ignorant of the photosensitive processes of animals at levels of organization below that of the image-forming eye, and an analysis of the properties of these simpler types of receptors offers one of the most promising approaches to an understanding of the common pattern of photoreceptor processes in general.
The Fertilization Reaction in the Sea-Urchin Egg. The Effect of Nicotine
Authors: Rothschild Lord , Swann M. M. 
Published: April 2021

ABSTRACT
Unfertilized eggs of Psammechinus miliaris which have been allowed to stand in sea water containing nicotine and are then inseminated in normal sea water are polyspermic. Polyspermy is not due to an increase in the speeds at which spermatozoa swim in these circumstances; nor to a decrease in the rate at which the change in cortical structure of the egg, the first sign of fertilization, is propagated over the egg surface. Experiments to test alternative explanations of the effect of nicotine have been carried out. The experiments do not enable a firm decision to be made between (a) a high-speed block to polyspermy (which has not been observed) with a high probability of a successful collision, and (b) a low-speed (20 sec.) block to polyspermy with a low probability of a successful collision.
The Determination of Sodium in Small Volumes of Fluid by Flame Photometry
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
A method of integrative flame photometry is described, by which the amount of sodium in biological fluids can be determined, using samples of the order of 10−3 cu.mm. With pure solutions of sodium chloride, of concentration from 0·05 to 2·0 %, the average error of the method is about 3 % of the concentration. When other substances are present systematic errors of up to 7·7 % have been recorded. The possibilities of reducing these systematic errors and of extending the method to deal with other elements are discussed.
Lipids of the Nervous System of the Squid Loligo Pealii
Authors: McColl J. D. , Rossiter R. J. 
Published: April 2021

ABSTRACT
Previous studies from this laboratory have indicated that the distribution of lipids in the mammalian central nervous system is very similar for a number of different species (Johnson, McNabb & Rossiter, 1948 a). The same is true for the lipids of peripheral nerve (Johnson et al. 1948 b). Johnson et al. (1949 a, b) concluded that free cholesterol, cerebroside and sphingomyelin are the principal lipids of the myelin sheath of a mammalian nerve fibre, although the recent work of Brante (1949) suggests that one of the components of brain kephalin, phosphatidyl serine, may also be present in considerable quantities in the myelin sheath. These lipids have been called the myelin lipids.
Giant Axons and Synergic Contractions in Branchiomma Vesiculosum
Authors: Nicol J. A. Colin 
Published: April 2021

ABSTRACT
Conduction in the giant axons of annelids has been clarified by the work of Stough, Eccles and colleagues, Bullock, Rushton and others (reviewed by Nicol, 1948a). They are now known to be motor axons, or at least nerve fibres on the efferent side of reflex arcs, and they intermediate quick withdrawal movements effected by synergic contractions of widespread longitudinal muscles. Probably the most highly developed axons of this kind occur in the Serpulimorpha (Nicol, 1948 a, b, c, d). Our knowledge of the physiological activity of these nerve fibres, as components of a neuro-muscular unit, is still incomplete, however, and the sabellid worm Branchiomma vesiculosum (Montagu) has been investigated, as a suitable experimental animal. The present paper gives an analysis of giant axon functioning in the intact animal as revealed through muscular activity. A few observations on the functioning of the giant fibres in Myxicola infundibulum (a related species) have already been published (Nicol, 1948 c), and will be referred to in the present account. Budington (1902) described the results of stimulating pieces of the earthworm which contained nerve cord. His records show contractions of the longitudinal muscles, and it is probable that he was stimulating the giant axons of the animal.
Osmotic Regulation in Mosquito Larvae: The Role of the Malpighian Tubules
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
The part played by the Malpighian tubules in the salt and water balance of Aedes aegypti larvae has been studied ; the intestinal fluid and haemolymph have been compared in respect of freezing-point depression and sodium concentration. It appears highly probable that the fluid passing down the intestine is derived from the Malpighian tubules with little or no contribution from the midgut. When the larvae are kept in fresh water the intestinal fluid is very slightly hypotonic to the haemolymph (not isotonic as previously reported), but its sodium concentration is only about one-half that of the haemolymph. When the larvae are kept in solutions of NaCl the difference in sodium concentration between intestinal fluid and haemolymph decreases. In an external medium of i % NaCl the difference is abolished. There is thus evidence that when the external medium is poor in salts the Malpighian tubules can contribute to the work of salt retention by excreting a fluid containing less sodium than the haemolymph; but there is no evidence that under any conditions they can excrete a fluid containing more sodium than the haemolymph. Evidence of a decrease in the sodium concentration of the tubule fluid from distal region to proximal region is not statistically significant.
The Variation in Fat and Glycogen Content of the Bot Fly (Gastrophilus Intestinalis) Larva Tracheal Organ During Development
Authors: Levenbook L. 
Published: April 2021

ABSTRACT
Numerous analyses on the chemical composition of various insects have shown that, as in mammals, fat and glycogen constitute the principal food reserves. Among holometabolic insects the accumulation of these two substances during the larval instars is, to a varying extent, utilized during the process of pupation. Most of the data on the chemical changes during metamorphosis are summarized by Needham (1942). However, as pointed out by Wigglesworth (1939), analyses of the body as a whole show only the gross alterations, and almost nothing is known concerning the composition of the separate organs. The only information available concerns the glycogen content of the isolated insect fat body; thus, Babers (1941) found that in the mature larva of Prodenia eridania (Lep.) the glycogen formed 23·3% of the fat body dry weight, while Yokoyama (1934) estimated the glycogen content of the silkworm fat body to vary from 2 to 17% of the dry weight according to age. No figures have been published for the fat content of the fat body, but histological evidence (Pardi, 1939; Wigglesworth, 1942) clearly demonstrates that fat is also present in high concentration.
Experiments on the Neural Crest of the Lamprey Embryo
Authors: Newth D. R. 
Published: April 2021

ABSTRACT
The fate of the neural crest of the head in Lampetra planeri has been studied by experiments involving the removal or the homoplastic transplantation of short regions of this tissue. The results show that the neural crest of lamprey is normally destined to form part at least of the dorsal root ganglia, and that it probably gives rise to most, if not all, of the melanophores and to some of the ectomesenchyme. No evidence that the neural crest of the head was the source of the ‘trabeculae cranii ‘or the cartilages of the branchial basket was found. It is concluded that these structures are most probably not crest derivatives. The phylogenetic significance of the embryology of the lamprey ‘trabeculae cranii’ and visceral skeleton is discussed. The transplantation experiments provided some evidence that the form of the neural tube in lamprey is determined in the same manner as that established by Holtfreter (1933, 1934) for Amphibia.
On The Hormonal and Neural Control of the Release of Gametes in Ascidians
Authors: Carlisle D. B. 
Published: April 2021

ABSTRACT
It is argued that the neural gland ( + ciliated pit) of ascidians is homologous with the entire pituitary of vertebrates, adenohypophysis as well as neurohypophysis. Ciona and Phallusia are shown to respond to an injection of chorionic gonadotrophin by the release of gametes. They respond in the same way to feeding with eggs and sperm of their own species but not to those of other species. This response is prevented in both cases by section of the nerves from the ganglion to the region of the gonads. Destruction of the heart and removal of the blood does not prevent the response to feeding with gametes, nor to injection of gonadotrophin into the neural region; this operation does prevent the reaction if the site of injection is elsewhere. Destruction of the neural gland, leaving the ganglion intact, prevents the response to feeding with gametes, but does not prevent its following an injection of chorionic gonadotrophin. The hypothesis is advanced that the neural gland ( + ciliated pit) is the sense organ involved in this response to feeding, and that it produces gonadotrophin and passes it to the ganglion by a non-vascular route; the ganglion then stimulates by nervous pathways the gonads to release gametes. It is suggested that gonadotrophin is here fulfilling a sensory role in passing information from sense organ to the central nervous system. It may be contrasted with adrenalin which passes instructions from the central nervous system to effectors. Phallusia is shown to respond with gamete release to an injection of an extract of the neural complex of Ciona.
The Excretion of Sodium and Potassium by the Malpighian Tubules of Rhodnius
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
The very considerable changes in the concentrations of sodium and potassium in the urine of Rhodnius during the normal course of excretion are not reflected in the haemolymph which remains relatively constant in composition. The concentration of potassium in the haemolymph can be increased some tenfold by adding potassium chloride to the blood on which the insect feeds. Such increase in the concentration of potassium can be tolerated for several hours without loss of nervous co-ordination, but it is ultimately fatal. The upper portion of the Malpighian tubule can secrete a urine which contains more potassium and less sodium than the haemolymph. During the passage of this urine through the lower portion of the tubule the differences in concentration between urine and haemolymph became reduced. It is probable that water and sodium, but not potassium, are reabsorbed from the urine in the rectum during the later stages of excretion.
An Electron Diffraction Study of the Structure and Orientation of the Lipids in Yeast and Bacterial Cell Walls
Authors: Hurst H. 
Published: April 2021

ABSTRACT
While it is generally agreed that many of the permeability relationships of different types of living cells depend on the chemical and physical properties of the lipids or lipo-proteins in the surface layers, no direct evidence of the nature of the molecular organization of these fatty components as they occur in situ has yet been produced. Such suggestions as have been made have been based mainly on permeability studies of cells and model membranes, while examinations of the properties and behaviour of the isolated components by the sensitive monolayer technique (Schulman & Rideal, 1937) has proved a useful guide to the possible molecular structure of the cell membrane. Supporting evidence has been derived from polarization and electron microscopy, and from impedance and electrophoresis measurements. The thinness of the cell membrane has so far prevented direct study by X-ray diffraction, although this method of analysis has successfully been applied to the study of isolated fatty components (Schmitt & Palmer, 1940).
A Comparative Study of the Lipids of the Vertebrate Central Nervous System
Authors: McColl J. D. , Rossiter R. J. 
Published: April 2021

ABSTRACT
Previous studies from this laboratory have shown that the distribution of lipids in the brains of a number of different mammalian species is very similar (Johnson, McNabb & Rossiter, 1948). Evidence was presented for the view that free cholesterol and the two sphingosine-containing lipids,* cerebroside and sphingomyelin, are the principal lipids of the myelin sheath of a mammalian nerve fibre (Johnson, McNabb & Rossiter 1949a, b, 1950; Burt, McNabb & Rossiter, 1950). These lipids were called the myelin lipids. However, McColl & Rossiter (1950, 1951) showed that the lipids of the nervous system of certain invertebrates, notably Loligo, Limulus and Libinia, differed in a number of respects from those of the mammal.
In this paper, data are presented for the lipids of the brains of a series of vertebrates, including representatives of the cartilaginous and bony fishes, amphibians, reptiles, birds and mammals.
A Roundabout for Studying Sustained Flight of Locusts
Authors: Krogh August , Weis-Fogh Torkel 
Published: April 2021

ABSTRACT
The purpose of the technique described here was to study the influence of external factors upon the flying speed and the ability of small ‘swarms’ of locusts to sustain prolonged flight. The wind forces acting on a flying animal depend only on the motion of its elements relative to the air mass, i.e. on the relative wind. Instead of investigating actual free flight, a locust can therefore be suspended in front of a wind tunnel and made to fly against a streamlined and uniform current of air, the wind speed being adjusted so as to correspond to the air speed of the freely flying insect. Under such conditions it has been possible to make a single individual fly for several hours. But a very large tunnel would be necessary for a number of animals to fly simultaneously as is required for quantitative work. Instead of moving the air mass, one can move the suspended animal through still air with a speed corresponding to the flying speed and so have several insects flying at once. Thus proper aerodynamic conditions for flight can be obtained by attaching the animals to a revolving ring, provided the ring is made so large that the angular velocity is kept small.