bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wall Drag On Free-Moving Ciliated Micro-Organisms
Authors: Winet H. 
Published: April 2021

ABSTRACT
It is generally assumed that wall drag on free-moving, self-propelled or passively moving micro-organisms is not significant under normal observation conditions. Yet the point at which such drag becomes significant has not been determined quantitatively.
By comparing the relative velocities of sinking as well as swimming ciliates in tubes of various bore widths it has been determined that wall drag on sinking cells is about 8 % significant at 10–132 body radii (or minor semi-axes) from the cell surface while the corresponding range for swimming cells is less than 1–4·2 body radii.
These results are compared with the mathematical approximations for Stokes radius Rs and depth of penetration of diffusing vorticity δ which characterize steady and quasi-steady Stokes flow respectively around a solid body. It is found that the asymptotic nature of the velocity profile of steady flow is reflected in the lack of agreement between Rs and the measured distance for 8 % drag. Conversely, the sharp gradient (or propulsive envelope) of the quasi-steady velocity profile is reflected in the substantial agreement between 8 and the measured distance for &gt; 0 % drag.
It is suggested that the given formula for 8 which includes allowance for a propagated wave is a valid measure of the thickness of the quasi-steady region and that observations on motile ciliates be restricted to organisms at least 4 cell radii from the nearest wall if measurements free of wall-drag effects are to be obtained.
On Ligature of the Vas Deferens in the Cat and Researches on the Efferent Ducts of the Testis in Cat, Rat and Mouse
Authors: Cunningham J. T. 
Published: April 2021

ABSTRACT
In a previous paper, June 1927, I described and discussed experiments on artificial cryptorchidism and ligature of the vas deferens in rabbits. The present paper deals with one experiment on ligature of the vas deferens in the cat and several experiments on ligature of the vasa efferentia in the rat, together with a microscopic investigation of the origin, course and structure of those ducts and of the successive parts of the epididymal tube.
The Rôle of Water in the Evolution of the Terrestrial Vertebrates
Authors: Gray J. 
Published: April 2021

ABSTRACT
The origin of truly terrestrial vertebrates was associated with the development of a skin which is relatively impermeable to water. The skins of fishes and of most amphibia are freely permeable to water, and water is readily lost when the animals are exposed to ordinary atmospheric conditions. The skin of a lizard on the other hand is relatively impermeable to water and the animal is therefore able to withstand exposure to air without serious inconvenience. Complete adaptation to terrestrial conditions involved the capability of laying and incubating eggs on land. The eggs of fish and of typical amphibia absorb, during development, considerable quantities of water from the external environment. The embryos of reptiles and of birds derive the equivalent of this water from the albumen layer secreted round the ova by the walls of the oviduct. Evidence is presented to show that the reptilian type of egg is to be derived from that of a dipnoan or amphibian, where the egg is surrounded by a mucilaginous or albuminous secretion of the walls of the oviduct. The mammalian egg can be derived from that of a reptile by supposing that the aqueous secretions of the oviduct are passed direct into the embryo instead of forming a separate phase round the ovum. An intermediate type is found in Monotremes where the secretions are passed into the ovum itself before the egg is laid.
An Experimental Examination of the Evidence for the Presence of Phosphatides in the Limiting Surface of the Living Protoplast
Authors: Steward Frederick Campion 
Published: April 2021

ABSTRACT
An outstanding problem of plant physiology is the nature of the mechanism which controls the movement of water-soluble substances into, and out of, the living cell. Recent investigations confirm the long established impression that in the vacuolar sap of living cells substances are present, which, although soluble in water, are almost unable to diffuse out when the cell is surrounded by water. It is clear that the living protoplast is responsible for this, since complete permeability is associated with death. Moreover, it is well established that the degree of permeability of living cells to solutes is dependent upon the composition of the medium with which they are in contact, and its consequent effect upon the plasma surface. Leaving on one side the controversy concerning the existence and constitution of a specific plasma membrane, which may be. responsible for these attributes of living cells, it is clear that the phenomena associated with boundary phases give adequate grounds for anticipating that the external surface of the protoplast will have a different composition from the main protoplasmic mass. It is natural that the composition of this surface layer should be stressed in theories of cell permeability, but it is clearly undesirable that our knowledge of its nature should rest largely on speculation.
On the Fixation of Atmospheric Nitrogen by Phoma Radicis Callunae, Including A New Method for Investigating Nitrogen-Fixation in Micro-Organisms
Authors: Jones W. Neilson , Smith M. Llewellyn 
Published: April 2021

ABSTRACT
(1) Evidence from chemical analyses of seeds of Calluna mdgaris and of seedlings grown on a nitrogen-free medium confirms the view that this plant can obtain nitrogenous supplies from the air, probably in the form of molecular nitrogen, in sufficient amount to prevent the advent of any symptoms of nitrogen starvation. (2) A new apparatus for the investigation of nitrogen-fixation by micro-organisms is described. (3) Using the above apparatus, experiments on the mycorrhizal fungus of Calluna vulgaris are described in which this organism was grown in pure culture on a nitrogen-free medium with and without a supply of molecular nitrogen. The evidence obtained indicates that the amount of glucose used by the fungus during growth, and the amount of nitrogen contained in the culture at the end of the growth period are greater under the former condition. It is concluded that the fungus in question can utilise the molecular nitrogen of the air in some degree under the conditions of the experiments, although these were not the most favourable possible for nitrogen-fixation.
It is considered that the results obtained justify an extension of these experiments using a strain of the fungus freshly extracted from the Calluna plant.
Rhythmic Susceptibility Changes in the Cleaving Arbacia Egg
Authors: Page Irvine H. 
Published: April 2021

ABSTRACT
The fertilisation reaction initiates a remarkable series of events in the egg. Lyon(1) first showed that Arbacia eggs were especially sensitive to heat just before cleavage and most resistant 10–20 minutes after fertilisation. However, the susceptible period for cold seemed to be quite different from that for heat, being almost exactly the same as the resistant period for heat. He (2) further found that eggs were especially susceptible to M/100-M/200 KCN about 10–15 minutes after fertilisation and that the resistance gradually rose as the time for the first cleavage approached.
Temperature and Heart-Rate in Fundulus Embryos
Authors: Glaser Otto 
Published: April 2021

ABSTRACT
On the 4th day after fertilisation, cardiac rhythm in Fundulus embryos, in all probability, is myogenic. Between 5 ° and 25 ° C., one of two temperature characteristics prevail and fluctuate either about μ = 16,300 or 14,300. On the 12th day, embryos, presumably neurogenic, expose prevailing increments of 20,900 or occasionally of 18,200. A definite critical region is localised about 20 ° where the prevailing increments break to the orders 16,000, 14,000 or 12,000. Over the corresponding range embryos about to escape from the egg-case, exhibit, in the only two instances recorded, μ = 23,000, 20,900 and 16,300. On presumable restoration of myogenic conditions in embryos of the 12th day, μ may be 14,300 over the entire range. The frequency of μ = 14,300 is greater than in normal larvae of the same age, whereas μ = 20,900 is restricted to the lower temperatures. In their bearing on the differences between myogenic and neurogenic rhythms, these results become explicable if we imagine an underlying mechanism identical for both cases. The same increments either occur or suggest themselves at all stages of development, or, if at times some appear to be distinctive of neurogenic Fundulus, these can be promptly duplicated from the list of increments shown by myogenic Limulus, e.g. 20,900. Clearly, however, the most frequent characteristics found belong to categories exposed by a great variety of biological acts, and their association in cardiac rhythms is common. These two facts harmonise well with the recent work on the metabolism of muscle and nerve.
The Significance of the Bohr Effect in the Respiration and Asphyxiation of the Squid, Loligo Pealei
Authors: Redfield Alfred C. , Goodkind Robert 
Published: April 2021

ABSTRACT
In 1904 Bohr, Hasselbalch and Krogh showed that carbon dioxide diminished the affinity of haemoglobin for oxygen. This phenomenon, known as the “Bohr effect,” together with the reciprocal effect of oxygenation upon the combination of carbon dioxide with blood, discovered by Christiansen, Douglas and Haldane (1914) must be taken into account in all quantitative considerations of the respiratory function of the blood of mammals. It is now recognised that the effects of carbon dioxide are not specific, but are due to alterations in the acid-base equilibrium of the blood and may be produced by other acids. The phenomena have also been described in the case of the blood of the lower orders of vertebrates (Krogh and Leitch, 1919; and Southworth and Redfield, 1926) and of the body fluids of invertebrate animals, such as the worms which have respiratory pigments more or less closely related to haemoglobin (Barcroft and Barcroft, 1924).
The Effect of Testicular Extracts on the Blood Calcium
Authors: Mirvish L. , Bosman L. P. 
Published: April 2021

ABSTRACT
It has long been recognised that the testis has an influence upon growth in general, and especially upon the growth of bone. This was the basis for the generalisation formulated by the early observers that growth and reproduction are essentially opposed to one another. Later investigations indicated, however, that the changes produced by castration are not due to the abolishing of spermatogenesis but to the fact that the normal internal secretion of the testis is not available for controlling the growth of bone.
The Metabolic Gradient and its Applications
Authors: Parker G. H. 
Published: April 2021

ABSTRACT
In Nereis virens the rate of carbon dioxide discharge for the whole worm is roughly o ·01 milligram of gas per gram of worm per minute. In similar terms the rate for the mid-trunk is a little over 0 ·01 milligrams and that for the head and tail regions about half of this rate. In Planaria maculata large worms (87 mgm.) show a lower rate of carbon dioxide discharge (0 ·0050 mgm. per gram of worm per minute) than small ones (55 mgm.) (0 ·0069 mgm. per gram of worm per minute). Also normal worms have a lower rate (0 ·0050 mgm.) than cut worms (0 ·0063 mgm.). Planarians cut transversely into halves, quarters or sixths show in such fragments so uniform a rate of carbon dioxide discharge that there is no reason to believe that the rate is really different in different parts. In the actinians Sagartia luciae and Metridium marginatum the rate of discharge of the oral halves is indistinguishable from that of the aboral halves and these two rates are very close to the rates of the animals as wholes. These results point to the absence of the assumed metabolic gradients in Nereis, Planaria and the actinians. Hyman’s results on annelids with the susceptibility method were obtained on Nereis but are believed to be due to differential penetration and are not accepted as a proof of a metabolic gradient. Hyman and Galigher’s results on annelids involve a misuse of the Winkler method. Shearer’s results on earthworms apply only to the head and tail ends and should have been supplemented, to be conclusive, with determinations for the mid-trunk. Metabolic gradients if present are not factors in morphogenesis but are at best measures of activity which may serve as features in the description of organisms.
The Anatomy of A Locust Visual Interneurone; the Descending Contralateral Movement Detector
Authors: O ‘shea M. , Rowell C. H. F. , Williams J. L. D. 
Published: April 2021

ABSTRACT
The DCMD neurone is physiologically well-known and runs from the brain to the metathoracic ganglion. It responds to novel movement of small contrasting objects in the visual field and synapses on metathoracic motoneurones which mediate the jump of the locust. Its anatomy, here reported, has been visualized by intracellular cobalt staining. The soma is 50μm in diameter and lies on the upper posterior face of the protocerebrum, lateral to the midline. A neurite runs to a thickened integrating segment 20 μm in diameter, which bears numerous dendrites ; none of these extends to the optic lobe. An axon leaves the integrating segment, crosses the brain, thickens to about 17 μm and descends the contralateral nerve cord. The descending axon terminates in the metathoracic ganglion, where it has three major branches both ipsi-and contralateral. Its branching in the mesothoracic ganglion is similar, but extends only ipsilaterally; in the prothoracic ganglion there is reduced branching, and in the suboesophageal ganglion none at all. The branching pattern in the metathorax is compatible with, and entirely explicable by, the known synaptic connexions with motoneurones. The morphological description of the cell has made possible intracellular recording from axon, integrating segment and soma.
Command Fibres in the Circumoesophageal Connectives of Crayfish
Authors: Bowerman R. F. , Larimer J. L. 
Published: April 2021

ABSTRACT
Command interneurons from the circumoesophageal connectives of crayfish which are capable of evoking various cyclical, phasic behavioural outputs are described. By pooling evoked-behaviour data and information on command-fibre location for a number of preparations it has been possible to repeatedly identify certain individual interneurons. Five escape or swimming-command identities have been established. Electrical stimulation of any of these elements activates the fast abdominal musculature, generating single or multiple tail-flips. Three forward-walking identities have been established within the experimental connective. Stimulation of a forward-walking command fibre results in extension of the abdomen and chelipeds in conjunction with locomotory movements of the walking legs. Output has been characterized as walking by virtue of the fact that the walking wheel is actually rotated by the stepping appendages. Four backward-walking identities have been established. For these command elements a variety of cheliped and abdominal geometries are superimposed on the basic backward-stepping patterns of the walking legs. Cyclical command fibres capable of evoking branchiostegite scratching, feeding-Fike activity, cleaning of the dorsal aspect of the abdomen, and slow rocking of appendages have also been noted.
A Study of the Malpighian Tubules of the Pill Millipede, Glomeris Marginata (Villers)
Authors: Farquharson Patricia Anne 
Published: April 2021

ABSTRACT
The Malphigian tubules of the pill millipede, Glomeris marginata are described. After the necessary analyses of the haemolymph had been carried out a Ringer solution was prepared which would support the secretion of tubule fluid in vitro. The reasons for the variation and deterioration in the secretion rates of control tubules are discussed. The presence of various amino acids in the bathing medium appears to be essential for fluid production. There would not appear to be a diuretic hormone involved in the control of secretion; and 5-HT, cylic AMP and theophylline will not stimulate fluid production. Secretion is inhibited by the metabolic inhibitors 2,4-DNP, azide and cyanide. The relative insensitivity shown to the latter two compounds is probably associated with a resistance mechanism.
Theory of CO2 Exchange in Trout Gills*
Authors: Cameron James N. , Polhemus John A. 
Published: April 2021

ABSTRACT
A computer simulation of countercurrent CO2 exchange in fish gills was constructed to examine effects of variations in blood and water flow rates. CO2 output was sensitive to both blood and water flow rates, contrary to experimental data. Various explanations of the contradiction are discussed, including patterns of gill perfusion and possible shunting of blood. A simplified version of the model was also used to demonstrate extreme sensitivity of COS efflux to variations of the residence time of blood in the gills. Data from the literature on reaction rate constants for the CO2/carbonate/ bicarbonate system are summarized, and the importance of some of these reactions is examined.
Analysis of the Electrophysiological Responses of the Trochanteral Hair Receptors of the Cockroach
Authors: Spencer H. J. 
Published: April 2021

ABSTRACT
In arthropods much of the body surface bears innervated hairs or bristles which have the general histological structure described by Snodgrass (1935) as sensilla trichoidea, and it is generally assumed from their positions that they are either mechanoreceptors or chemoreceptors. A number of studies have shown that tricho sensilla of similar histological structure respond to very different sensory modalities and that to some extent the receptor response spectrum is determined partly by the structure of the hair and partly by the characteristics of the innervating neurone (Dethier, 1963).
Command Fibres in the Circumoesophageal Connectives of Crayfish
Authors: Bowerman R. F. , Larimer J. L. 
Published: April 2021

ABSTRACT
Several discrete postures have been generated by electrical stimulation at frequencies of 20–75 Hz of command interneurons within the circumoesophageal connectives of the crayfish. The behaviour patterns were recorded by cine photography. The similarity of the patterns in different individuals generated by stimulation of interneurons found in the same positions within the cord, strongly suggested that certain of the interneurons examined in this study were identical. A number of tonic command fibres were found, each of which evoked a specific body geometry. Tonic command units were classified on the basis of evoked cheliped, walking leg, and abdominal positions. The study concentrated on those command fibres which generated spatially distributed behaviour patterns involving both abdomen and appendages, and neglected command elements with more restricted outputs. The types of tonic command fibres characterized include the following: bilateral appendage promotion, ipsilateral appendage promotion, bilateral cheliped lift, ipsilateral appendage lift and flex, general flexion, abdominal extension, and both ipsilateral and contralateral turning. A movement-suppressing command fibre, ultimately termed the ‘statue fibre’ was found twice. Stimulation of this element terminated spontaneous activity by ‘freezing’ the animal, irrespective of position. An additional consequence of stimulation of the statue fibre was the overriding of the excitatory effect of mechanical stimulation which in the absence of the command drive would provoke the animal into activity. It is suggested that a restricted number of tonic command fibres could be functionally operative in the generation of their corresponding behaviour patterns. For the majority of tonic command fibres, however, it is felt that the unit is merely one of a group of elements each of which is activated simultaneously or sequentially for discrete behavioural performances.
Electrophysiological Responses of the Terminal Sensilla on the Maxillary Palps Of Locusta Migratoria (L.) To Some Electrolytes and Non-Electrolytes
Authors: Blaney W. M. 
Published: April 2021

ABSTRACT
Three morphologically and functionally different types of sensilla on the maxillary palp tips of Locusta migratoria are distinguished and an electrophysiological study is made of the most commonly occurring type. Responses to stimulation with 0·1 M sodium chloride show impulses of one, two or three amplitude categories in different sensilla. Variability of response to a constant stimulus is appreciable, both between and within sensilla. Tests with a range of compounds indicate that individual neurones are capable of responses to compounds of different chemical classes. Specificity of sensilla is more marked than specificity of neurones. Methods of interpretation of results are evaluated and the results are discussed in the context of discrimination of food plant materials.
The Response of the Swim Bladder of the Goldfish (Carassius Auratus) to Acoustic Stimuli
Authors: Popper Arthur N. 
Published: April 2021

ABSTRACT
The teleost swim bladder is a gas-filled chamber located in the abdominal cavity just below the vertebral column. It consists of one or more inter-connected chambers which may be partially divided into ‘subchambers’ by septa that are extensions of the inner lining of the swim-bladder wall (Demski, Gerald & Popper, 1973 ; Greene, 1924; Tavolga, 1962 and others).
The Effect of Swimming Activity and Section of the Vagus Nerves on Heart Rate in Rainbow Trout
Authors: Priede Imants G. 
Published: April 2021

ABSTRACT
Heart rates associated with swimming activity were measured in intact and vagotomized fish at 6·5 and 15 °C. Low swimming speeds had no effect on heart rate but above a threshold speed it increased logarithmically with swimming speed up to the critical speed and maximum heart rate. Times for recovery after exercise increased rapidly above the critical speed. Bilaterally vagotomized fish at 6·5 °C showed high resting heart rates and erratic cardiac responses to exercise. In bilaterally vagotomized fish at 15 °C heart rates were normal except for a low maximum rate. It is concluded that the vagus nerve can function differently at different temperatures.
Light-Evoked Electrical Potentials from the Eye and Optic Nerve of Strombus: Response Waveform and Spectral Sensitivity
Authors: Gillary Howard L. 
Published: April 2021

ABSTRACT
The neural processing of visual information by the retina is reflected in the light-evoked extracellular retinal potentials (electroretinogram or ERG) and the discharge pattern of the concomitant afferent impulses in the optic nerve fibres. The waveform of the ERG is often fairly complex, since it represents the summed activity of a large number of different neurons; this activity can include the photic stimulation of receptors, and synaptic excitation and inhibition (Brown, 1968; Werblin & Dowling, 1969). Examining the ERG and its relation to the optic nerve activity which encodes the visual information can help to reveal the underlying neural mechanisms (Kennedy, 1964). Molluscan eyes, which exhibit a vast range of anatomical complexity (Charles, 1966), have proven amenable to the electrophysiological investigation of these mechanisms (see Discussion for examples and references).