bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Atrial Nervous System of Amphioxus (Branchiostoma)
Authors: Holmes William 
Published: April 2021

ABSTRACT
This paper is concerned with the system of neurons which lies in the walls of the atrium of Branchiostoma.
The system is found on the parietal and ventral walls of the atrium, as well as round the gut, and it is therefore thought preferable to speak of it as the atrial nervous system rather than the autonomic (enteric) system (Boeke).
The neurons are shown to lie in or immediately below the atrial epithelium, which is of ectodermal origin.
Special attention is given to the innervation of the gut and its diverticulum, of the atrio-coelomic funnels, and of the atrioporal region.
Evidence as to the effector and receptor elements of the system is discussed. It has central connexions, and it is suggested that its activities play an important part in the animal’s behaviour.
Undulatory Propulsion
Authors: Gray J. 
Published: April 2021

ABSTRACT
1. Typical undulatory progression over a rigid environment depends on three fundamental factors:
(i) Internal bending couples change the lateral curvature of each region of the body to that previously characteristic of the region lying immediately anterior to itself.
(ii) The phase of lateral bending varies along the length of the animal’s body.
(iii) The presence of external restraints prevents all regions of the body from moving along any path other than one tangential to their own circumference of curvature.
2. The magnitude of the forward tangential thrust imparted to the body depends on (a) the magnitude of the internally generated bending couples, and (b) the form of the waves. If friction operates on the surfaces of external restraint the thrust also depends on the coefficient of lateral friction and on the position of the restraints.
3. From a mechanical point of view, an undulating organism (irrespective of its size and internal structure) can be regarded either as a series of curved levers or as a series of inclined planes.
4. The general principles of undulatory swimming are the same as for a terrestrial glide, except for the fact that each element of the body must possess a component of motion normal to its surface if it is to contribute towards the propulsion of the animal; this type of motion can only occur when the waves move backwards relative to the ground. The animal cannot move forward as fast as the waves are propagated over the body.
5. The propulsive powers of three-dimensional waves are limited to the extent to which the organism is restrained by external forces from spinning about its own longitudinal axis. Otherwise the principles of progression are the same as for twodimensional waves: the resultant of all the forces acting normally to the body is equal but opposite to that of all tangential forces.
The Effect of Phenylthiourea on Pigmentation by Melanin in the Developing Frog, Eleutherodactylus martinicensis
Authors: Millott Norman , Lynn W. Gardner 
Published: April 2021

ABSTRACT
The black pigment cells in the skin, iris, and retina of Eleutherodactylus martini-censis (Tschudi) are melanophores. Under the influence of 0·01 percent, phenylthiourea the melanin disappears in about 84 hours at laboratory temperatures. After administration of the substance for 5 days, discontinuance of treatment is followed by return of the pigment within 72 hours, to an extent at least equal to that normally attained in untreated controls. The stages of disappearance and reappearance of this pigment have been studied in the gross embryo, skin, iris, and retina, as well as in individual melanophores.
Observations on the Nerve Fibres of Aurellia aurita
Authors: Horridge Adrian 
Published: April 2021

ABSTRACTThe nerve fibres of Aurellia aurita were originally described by E. A. Shafer from gold preparations. This work has been repeated with Holmes’s method of silver staining on the slide. Results have beert obtained substantially in agreement with those of Shafer.The same nerves can be seen in the living animal when a phase-contrast microscope or oblique illumination is used. By the use of these techniques, a study has been made of the plan of the nerve net over the subumbrellar surface of the bell.This work is intended as an anatomical foundation for physiological studies to be described elsewhere.
Spicule Form in Leucosolenia complicata
Authors: Jones Walter Clifford 
Published: April 2021

ABSTRACT
The tri- and quadriradiates of Leucosolenia complicata are described in four aspects: surface view, transverse view, side view, and planar view. The spicule form and size vary with the distance from the oscular edge in all four cases.
In planar view (when the eye is directed along the optic axis) the spicule rays usually appear straight and thus exhibit a tendency to grow in planes which intersect in a line having the direction of the optic axis. The angle between the oscular ray planes (the planar angle) is always greater than 120° and the spicules hence belong to the ‘secondary sagittal’ class of von Ebner. The planar angle is not closely correlated with the optic angle and varies from about 160° at the oscular edge to about 140° at the base of the tube. This variation precludes the possibility that the angle is simply controlled by the crystallizing properties of calcite.
The curvature of the choanoderm is a factor controlling spicule form because the formative calcoblasts move in contact with this layer when secreting their respective rays.
Reasons are given for returning!,, coriacea (Montagu) to a separate genus, Clathrina.
The Mechanism of Proboscis Movement in Arenicola
Authors: Wells G. P. 
Published: April 2021

ABSTRACT
The mechanism of proboscis movement is analysed in detail in Arenicola marina L. and A. ecaudata Johnston, and discussed in relation to the properties of the hydrostatic skeleton.
Proboscis activity is based on the following cycle of movements in both species.
Stage I. The circular muscles of the body-wall and buccal mass contract; the head narrows and lengthens.
Stage IIa. The circular muscles of the mouth and buccal mass relax; the gular membrane (or ‘first diaphragm’ of previous authors) contracts; the mouth opens and the buccal mass emerges.
Stage IIb. The longitudinal muscles of the buccal mass and body-wall contract; the head shortens and widens and the pharynx emerges.
Stage III. As Stage I.
The two species differ anatomically and in their hydrostatic relationships. In ecaudata, the forward movement of body-fluid which extrudes and distends the proboscis is largely due to the contraction of the gular membrane and septal pouches. In marina, the essential mechanism is the relaxation of the oral region which allows the general coelomic pressure to extrude the proboscis. The gular membrane of marina contracts as that of ecaudata does, but its anatomy is different and it appears to be a degenerating structure as far as proboscis extrusion is concerned.
Withdrawal of the proboscis may occur while the head is still shortening and widening in Stage 116, or while it is lengthening and narrowing in Stage III. The proboscis is used both in feeding and in burrowing; in the latter case nothing enters through the mouth; the difference is largely caused by variation in the timing of withdrawal relative to the 3-stage cycle.
Experiments on the Mechanism of Silver Staining: III. Quantitative Studies
Authors: Peters A. 
Published: April 2021

ABSTRACTThe quantitative aspects of silver staining of sections have been investigated with radioactive silver (Ag111). The concentrations of reducible silver, developed silver, and silver nuclei in the sections were determined, but it is doubtful if the values obtained for silver nuclei are significant.All three forms of silver increased with pH, time, and the concentration of silver in the impregnating solution. Temperature of impregnation had little effect on the uptake of reducible silver, but increased the developed silver, presumably by increasing the silver nuclei. An increase in the temperature of a hydroquinone-sulphite developer increased the amount of reducible silver reduced by the developer. The deposition of silver by a glycine physical developer was shown to follow a curve which was reasonably consistent with the assumption of a typical autocatalytic reaction.The uptake of silver by non-nervous tissues provided evidence that the process is not specific for nerves; the final specificity of staining is determined during development.The quantitative results are consistent with the hypothesis that the histidine in the sections is responsible for the combination of reducible silver.
Experiments on the Mechanism of Silver Staining: IV. Electron Microscope Studies
Authors: Peters A. 
Published: April 2021

ABSTRACTSilver-stained sections of nervous tissue were examined with an electron microscope. It has been shown that the developed silver is particulate. These particles are between 30–700 Å in diameter and in nerve-fibres they are disposed along the surface and inside the components of the fibre. When impregnated sections were developed in a glycine physical developer, the mean size of the developed silver particles increased with an increase in the time of development.In silver-stained sections of human sympathetic ganglion, the silver particles were distributed throughout the cell, but were more densely aggregated in the cell membrane and the nucleus. Erythrocytes show a dense aggregation of silver particles throughout the cytoplasm.
Studies of the impregnation of nervous tissue elements: I. Impregnation of axons and myelin
Authors: Wolman M. 
Published: April 2021

ABSTRACT
All metallic impregnation methods depend on the presence of reducing groups in tissues. By testing the effect of various reduction indicators on sections of nervous tissue it was found that some reduction systems do not have a high enough oxidizing potential to serve for the visualization of either axons or myelin. Others can visualize myelin sheaths. The systems having the highest potential visualize also axons. Although myelin can be oxidized more easily than axons, axons are probably relatively richer in reducing groups.
Impregnation by AgNO3 or Ag-diammine results in the formation of silver nuclei in both axons and myelin. Subsequent exposure of such sections to the action of reducing agents increases the visible impregnation of the axons much more than that of the myelin. This effect can be ascribed to the low dielectric constant of myelin.
Gold toning serves a dual purpose: (a) coating with gold the more heavily impregnated structures, and (b) clearing the background through the displacement of the silver from the less intensely impregnated areas.
The mechanism of metallic impregnations and the rationale of the different steps in Bielschowsky’s procedure for axons are discussed.
The Peri-renal Tissue of Protopterus A Contribution to the History of the Adrenal
Authors: Holmes W. , Moorhouse D. E. 
Published: April 2021

ABSTRACT
The animal studied, was the lungfish Protopterus aethiopicus; the investigation was histological and cytochemical, the material being freshly taken from East African lakes.
The peri-renal tissue is a substantial organ which, because it surrounds the kidney, extends through the greater part of the body cavity. Those who have investigated its structure in recent years have considered it to be a haematopoietic organ.
A wide variety of histological, histochemical, and haematological techniques was used. The organ is shown to contain five characteristic kinds of tissue; these are named: lipid, endothelial, pigmented, round-cell, and steroid tissue respectively.
The lipid tissue is characterized by cytoplasmic liposomes—droplets containing phospholipid. In one type of cell, the ‘small lipid cell’, which may be related to the eosinophil granulocytes of the blood, the droplets have a relatively small diameter. In a second type, the ‘large lipid cell’, the droplets grow to a much larger diameter, and show evidence of cycles of activity involving increase and disappearance of the phospholipid. Histochemical interpretations are made difficult by the finding that this phospholipid does not colour with Sudan black.
The endothelial tissue is composed of phagocytic (macrophage) cells some of which are elongated and line vascular sinusoids while others are spherical and contain larger inclusions. These inclusions have some lipid characteristics and may be a manifestation of the translocation of lipid within the organ.
The pigmented tissue is composed of melanophores and of a second, round, type of cell which shows evidence of relationship with the macrophage system. Both kinds of cell contain ‘melanin’; the second also has inclusions with different histochemical properties.
The round-cell tissue, found in nodules, has a general resemblance to lymphoid tissue. It is doubtful whether its cells are lymphocytes, but it has not been found possible to characterize them in any other way.
The steroid tissue is composed of cells which react positively to the histochemical tests comprised in the ‘steroid repertoire’, as used in the study of the mammalian adrenal.
Attention is drawn to technical difficulties which may have confused the study of the peri-renal tissue as a haematopoietic organ. The connexion between the lipid tissue and circulating granulocytes has features which distinguish it from the processes of granulocyte formation in the spleen.
There are strong indications of an evolutionary connexion between peri-renal tissue and the cortex of the adrenal gland of higher animals. The lungfish may offer the best starting-point for the study of the comparative histology of the adrenal of tetrapods. The association between lipid, steroid, haematopoietic, macrophage, and pigment tissue has parallels in function in the complex interrelations of the mammalian adrenal.
The Structure of the Corpus Allatum of Iphita limbata (Hemiptera)
Authors: Nayar K. K. 
Published: April 2021

ABSTRACT
The corpus allatum of Iphita limbata Stal. (Pyrrhocoridae, Hemiptera) is an unpaired, syncytial gland, with nuclei of two sizes. The allatic nerve transmits neurosecretory colloids into the gland. The recurrent nerve adjacent to the allatic nerve also contains neurosecretory products. The cytoplasm of the gland contains granular mitochondria which show a tendency to aggregate into clusters or rings and chains, and numerous tiny spheroids of variable size forming the lipochondria, which are sudano-phil, argentophil, and generally osmiophil. Vacuoles are present in the cytoplasm; these are surrounded by spheroids. The cytoplasmic content is rich in phospholipids. The gland is larger in the female. It gradually enlarges as the eggs develop and reaches its maximum size in the gravid female.
Further Observations on the Histochemistry of Fat Absorption in the Small Intestine of the Rat
Authors: Hewitt W. 
Published: April 2021

ABSTRACT
Studies have been made of the small intestine of rats previously fed with triolein. A previous description of the location of the lipid and phospholipid has been confirmed by using Sudan black and the acid haematein test. In addition histochemical tests have been applied to detect neutral fat and fatty acid. The lipid in the free border of the epithelial cells of the mucous membrane consisted of fatty acid and probably neutral fat, which would support the belief that when neutral fat is absorbed some of it is unhydrolysed. Additional evidence for this is provided by the fact that neutral fat could also be detected between the lateral parts of the cells. Occasionally fatty acid was also detectable in this location. Variable proportions of neutral fat, fatty acid, and phospholipid were to be found inside the epithelial cells and it appeared possible that there was a direct relationship between the amounts of neutral fat and phospholipid present.
Normal and Induced Degeneration of Abdominal Muscles during Metamorphosis in the Lepidoptera
Authors: Finlayson L. H. 
Published: April 2021

ABSTRACT
Certain segmental units of the three main longitudinal muscle-bands in the abdomen of the larva of Galleria, Platysamia, Telea, Antheraea, and Samia (Philosamia) do not degenerate during the histolytic phase in the prepupa and early pupa. In the 3rd abdominal segment the amount of muscle that persists is variable; in the 4th, 5th, and 6th segments, invariable. Apart from single pairs of transverse muscles in the 2nd and 3rd segments and those of the gut and heart there are no other muscles in the pupa. Vestiges of degenerated muscles are often found in the pupa.
The longitudinal muscles which survive the transformation of the pupa into the adult degenerate during the first z days of adult life.
Experiments were made on larvae, prepupae, pupae, and adults in attempts to influence muscle-degeneration and muscle-persistence. Extirpation of ganglia or severance of nerves in larvae and prepupae of Galleria caused the normally persistent muscles to degenerate during pupation. Controls in which larvae were dissected before pupation revealed no degeneration of denervated muscles. In saturniids denervation also resulted in degeneration or atrophy but only after a much longer period, a matter of several weeks instead of several days. Muscles may be affected by extirpation of ganglia or severance of nerves in segments preceding their own segment.
Previous workers have shown that the growth of the new adult muscles is dependent on the influence of the central nervous system. This is not so in the case of sheets of fine muscle-fibres lying under the epidermis of the adult. They develop in the absence of central innervation.
Operations which had no effect on muscle-degeneration in the adult included extirpation of ganglia in pupa and adult, beheading and bleeding, extirpation of corpora allata plus corpora cardiaca, ligations, extirpation of pupal gonads, and isolation of adult abdomens. Substitution of blood from diapausing pupae or saline for the adult blood in isolated abdomens was effective in slowing the process of muscle-degeneration. This result shows that the blood composition is of importance in the process of histolysis in the adult.
The previous work on the physiology of insect histolysis is briefly reviewed. The influence of the nervous system as described in this paper is discussed and related to similar findings in other arthropods and in vertebrates.
The Blood Vascular System of Nephtys (Annelida, Poly chaeta)
Authors: Clark R. B. 
Published: April 2021

ABSTRACT
The four longitudinal vessels of the circulatory system of Nephtys califomiensis are dorsal, sub-intestinal, and neural, the latter being paired. There is a complete longitudinal circulation; the dorsal vessel communicates with the sub-intestinal by way of the proboscidial circulation and with the neural by way of the circum-oral vessels. In each middle and posterior segment segmental vessels from each of the longitudinal trunks carry blood to and from the parapodia and body-wall. The segmental circulation is completed by a circum-intestinal vessel connecting the dorsal and sub-intestinal vessels in each segment and an intersegmental branch connecting the dorsal and sub-intestinal segmental vessels. A trans-septal branch of the neural segmental vessel communicates with the sub-intestinal segmental vessel. This arrangement is modified in anterior segments which house the muscular, eversible pharynx, and no blood-vessels cross the coelom except by running through the body-wall. On anatomical grounds and by comparison with other polychaetes it seems likely that segmental is subordinate to longitudinal circulation. There are no endothelial capillaries such as have been described in some other polychaetes; instead there are numerous blindending vessels the walls of which are composed of the same three layers as other vessels and which are probably contractile. The dorsal vessel, where it is in contact with the ventral surface of the supra-oesophageal ganglion, forms a plexus in close association with a modified part of the brain capsule and a special axonal tract within the ganglion. It is thought that by way of this ‘cerebro-vascular complex’, hormones produced in the neurosecretory cells of the brain pass into the blood-stream.
A simple apparatus for freezing-drying histological specimens
Authors: Kramer H. , Hill R. G. 
Published: April 2021

ABSTRACT
The construction and operation of a simple apparatus for freezing-drying histological specimens is described. The apparatus, which is constructed from materials readily available in most laboratories, requires neither elaborate pumping equipment nor vapour traps, for the water molecules emanating from the specimens are carried away by a stream of dry gas. By this means specimens can be dried from a lower temperature in a time considerably shorter than is possible with the more complicated and costly freezing-drying apparatus usually used.
The Antennal Pulsating Organs of Mosquitoes and other Diptera
Authors: Clements A. N. 
Published: April 2021

ABSTRACT
The antennal pulsating organ of mosquitoes consists of two vesicles, each sending a blood-vessel to the antenna of its side and each connected to the aorta by a muscle. Contraction of the muscle causes blood to enter the vesicle through a valve and relaxation allows an elastic contraction of the vesicle so that the blood is discharged through the blood-vessel to the antenna. The organ appears to be myogenic.
Antennal pulsating organs occur in most families of the Diptera Nematocera but not all, and a similar organ is present in Drosophila.
Observations on the stomach and digestive diverticula of the lamellibranchia: II. The nuculidae
Authors: Owen G. 
Published: April 2021

ABSTRACT
The anatomy and histology of the stomach and digestive diverticula and the physiology of digestion in the Nuculidae have been investigated.
The stomach is relatively large and possesses a well-developed style sac, although a rod-like crystalline style is absent. Sorting areas are present in the dorsal region of the stomach but the ciliary currents are relatively weak and have little effect on the ingested material.
The digestive diverticula consist of three regions, the physiological relations of which have not been fully elucidated. The three regions are: (a) a much-branched system of non-ciliated main ducts, the epithelium of which shows a well-developed brush-border; (b) short, unbranched ciliated secondary ducts; (c) irregularly branched blindly ending tubules. The epithelium of the tubules is divided into two regions, one composed of large cells containing numerous conspicuous granules and the other of less frequent and smaller darkly staining cells. Each darkly staining cell bears a single flagellum.
Separate mucous glands cannot be demonstrated in any part of the stomach or digestive diverticula.
The epithelium of the style sac secretes an amylase and a lipase. Extracts of the digestive diverticula contain an amylase, a lipase, and a protease.
Unlike the majority of lamellibranchs, fluid and solid particles do not appear to enter the digestive diverticula from the stomach and in no part of the gut or of the diverticula is there ever any evidence of intracellular digestion. It is suggested that in the Nuculidae digestion is exclusively extra-cellular and confined to the stomach. The soluble products are absorbed by the epithelium of the stomach and first part of the intestine.
The diverticula of the rest of the Lamellibranchia are compared with those of the Nuculidae. While the Nuculidae are in many respects primitive lamellibranchs, the conclusion is reached that the digestive diverticula present many specialized features possibly correlated with the method of feeding.