bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facilitation in Sea Anemones
Authors: Ross D. M. 
Published: April 2021

ABSTRACT
The previously reported effect of anemone extracts, the occurrence of quick closing responses to single electrical stimuli in Metridium, has been re-investigated. In standardized tests it was found that whereas hundreds of stimuli are required for each response to a single stimulus in untreated animals, after anemone extract the incidence of such responses is one per nine stimuli. The incidence of these responses falls off with decreasing doses of extract and the effect disappears when less than of the material from a single large Metridium is administered. There is no evidence that extracts from ‘stimulated’ and ‘unstimulated’ (i.e. anaesthetized or quick-frozen) anemones differ in potency. Extracts from divided animals show greater activity in the ‘sphincter-disk’ fraction. The incidence of the responses also falls off in time and is highest from 15 to 30 sec. after beginning the treatment. The effect is sporadic and short-lived and responses to two or more successive stimuli are exceptional. A number of treatments, such as drastic changes in pH, KC1(K+ × 8), tetramethylammonium hydroxide (1 : 100), NH4C1 (1 : 340) and especially bile salt and saponin, have similar effects. Drugs with neuro-muscular effects elsewhere (acetylcholine, adrenaline, tyramine, histamine, etc.) were generally ineffective except at very high doses. Food stimulants too were ineffective. From the time relations and other aspects of the responses to single stimuli it is concluded that the effect should not be attributed to a substance with the function of a ‘facilitator’ in the living animal. While the effects are consistent with the passage of occasional adventitious impulses in the nerve net, there is a singular absence of spontaneous or post-stimulus contractions. Certain implications of this feature of the results are discussed.
The Freezing, Drying and Storage of Mammalian Skin
Authors: Billingham R. E. , Medawar P. B. 
Published: April 2021

ABSTRACT
The viability and general preservation of skin that has been subjected in vitro to freezing, drying and other procedures may be tested by transplanting it back to the animal from which it was originally removed. Rabbit’s ear skin withstands either slow or rapid freezing down to the temperature of liquid air. Slow freezing gives better preservation than rapid freezing, but impregnation with glycerol solutions protects skin against some of the harmful consequences of rapid freezing. Epidermal melanoblasts do not withstand rapid freezing unless they have been protected by glycerol solutions. Rapid thawing gives better preservation than slow thawing. Malpighian cells of the epidermis survive slow thawing after impregnation with glycerol solutions but not after impregnation with Ringer’s solution. Skin slowly frozen after impregnation with glycerol solution and stored for 4 months at—79°C. was indistinguishable, on transplantation, from a freshly removed graft. The storage of skin at—79°C. does not result in progressive deterioration during the period of storage. It is shown that the toxicity of glycerol to the various cellular constituents of skin is so slight that it may be disregarded. Isolated epidermal cells withstand exposure to 98·1 % glycerol at room temperature for half an hour. Skin does not withstand dehydration to a degree that results in a final overall water content below about 25 %. Impregnation with glycerol solutions does not increase its capacity to withstand dehydration.
Preliminary Observations on the Mechanism of Cleavage in the Amphibian Egg
Authors: Waddington C. H. 
Published: April 2021

ABSTRACT
The formation of blastomeres by the newly fertilized egg has been studied by many authors, who have found the process a convenient avenue for attacking the general problem of cell division. By far the greater part of the work has been carried out on the eggs of marine invertebrates, and, in spite of their great suitability for most types of experimental embryological investigation, the eggs of Amphibia have not as yet been made much use of in this connexion. The nuclear phenomena attendant on fertilization and cleavage in the Amphibia have been rather fully described (see, for instance, Fankhauser & Moore, 1941), but a short note by Schechtman (1937) contains almost everything that we know about the cleavage of the cytoplasm, and the part played in it by cortical movements.
During the last two summers a few experiments have been made which show that the amphibian egg provides very favourable material for a direct attack on certain of the crucial problems of cell division, since not only is it rather easy to perform micro-surgical operations on the developing cleavage furrow in a manner which would be very difficult in the small eggs of most invertebrates, but the pigmentation of the surface allows the cortical movements to be followed precisely in time-lapse cinema films. These experimental opportunities have not yet been by any means fully exploited, but the preliminary experiments have already yielded certain results which it seems worth while to record.
The experiments were made with eggs of Triturus alpestris which were laid and fertilized normally in the aquarium. The eggs were observed in Holtfreter solution, either of normal strength, or diluted with an equal volume of distilled water.
The Preferences of Honeybees for Solutions of Various Sugars Which Occur in Nectar
Authors: Wykes G. R. 
Published: April 2021

ABSTRACT
In field and in laboratory experiments bees were offered equal volumes of sugar solutions, of different composition but the same total concentration. It was found that sugars which occur in nectar were not equally attractive to bees. Consistent preferences were shown for solutions of single sugars in the following descending order : sucrose, glucose, maltose, fructose. The acceptances of some mixtures differed from those predicted on the basis of an additive effect of the constituent sugars. Anomalous high preferences were shown for sucrose-glucose-fructose solutions. The concentration of the solution appeared to influence the observed preferences, the relative acceptances of solutions at normal threshold level differing from those at higher levels in the series of laboratory experiments. No direct relationship appeared to exist between the chemical constitution of the sugars offered and their acceptance by bees; and no evidence was found to explain the observed differences in preferences for solutions of either single or mixed sugars. Attention is drawn to the possible biological significance of such selective responses by bees—it appears that the sugar composition of nectar may be a contributory factor influencing the visits of bees to flowers.
Diapause in Lucilia Sericata (MG.) Diptera
Authors: Cragg J. B. , Cole Patricia 
Published: April 2021

ABSTRACT
Data collected over a period of 2 years have shown that diapause in 3rd-instar larvae of Lucilia sericata (Mg.) may be of maternal origin and that its incidence gradually increased in the latter part of the blowfly season. The age of female flies has no significant effect on the amount of diapause. The capacity to give diapausing batches was lost by the majority of flies kept under standard laboratory conditions for 10-16 days.
The Size of Ommatidia in Apposition Eyes
Authors: Barlow H. B. 
Published: April 2021

ABSTRACT
In a compound apposition eye the acuity may be limited by the interommatidial angle or by the optical performance of each ommatidium. In the honeybee the performance of the ommatidia must approach the theoretical limit set by diffraction if the whole eye resolves points separated by twice the inter-ommatidial angle. The eyes of twenty-seven other species of Hymenoptera were measured, and the results show that in eyes of different sizes the number of ommatidia is adjusted so that inter-ommatidial angle is just below the limiting resolving power of the ommatidia; this is the condition for optimum acuity in a compound apposition eye. When this condition is fulfilled the minimum resolvable angle is inversely proportional to the square root of the linear dimensions of the eye. Acuity increases with size more rapidly in the simple type of eye.
Studies on Insect Metamorphosis
Authors: Singh-Pruthi Hem 
Published: April 2021

ABSTRACT
Kellog and Bell (1904) working on the silkworms noticed that if they were fed on insufficient quantities of leaves, their larval life was prolonged, i.e., their pupation or metamorphosis was postponed. Northrop (1917) showed the same state of things in the flies, Drosophila, when reared on food containing little or no yeast. Then, Tangl (1909 (a) and (b)) observed that if the flies were bred on unsuitable food which they did not readily take, they pupated a week later than the normally fed individuals. Thus the researches of all these authors indicated that inadequate feeding, qualitatively or quantitatively, delays metamorphosis. But this general conclusion was contradicted by the works of Krizenecky (1914) and of Szwajsowa (1916) on mealworms (Tenebrio molitor) which pupated much earlier when starved. In order to determine how far the above mentioned general conclusion could be modified, several experiments have been performed on mealworms, of different stages of growth, the results of which are reported in the following pages.
The Structure of Chromosomes
Authors: Belling John 
Published: April 2021

ABSTRACT
When pollen-mother-cells (or young microspores) of a plant with large chromosomes are mounted in iron-acetocarmine (1), torn chromosomes usually appear to have the consistency of honey or glue, long curling threads extending out from the broken ends. The cytoplasm is more liquid (stage 1). In a day or two, however, the cytoplasm has usually attained the consistency of a firm jelly or of cheese, while the chromosomes are still harder (stage 2). In this state the cell contents may be squeezed flat by carefully graduated pressure, without injury to the chromosomes. In the course of time the hardening progresses, until both cytoplasm and chromosomes become more or less brittle under pressure (stage 3).
Counting Live and Dead Bull Spermatozoa
Authors: Campbell R. C. , Hancock J. L. , Rothschild Lord 
Published: April 2021

ABSTRACT
An investigation has been made into the accuracy of estimates of the proportions of dead spermatozoa in diluted and undiluted bull semen, using the nigrosineosin live-dead staining technique. Two operators counted 24,673 spermatozoa, in lots of approximately 200, on smears derived from a number of subsamples taken from the same ejaculate. The variations between different counts made on one smear were consistent with random sampling from a binomial population; the same applied to variations between slides made from one subsample; the variation between subsamples were, however, larger than would have been expected on the basis of random sampling. Undiluted semen and semen diluted 1/4 with Ringer-phosphate-fructose solution had the same mean percentage dead and precision of estimation. Tables are given showing how the precision of an estimate of the proportion of dead spermatozoa in a sample varies according to the percentage of dead spermatozoa, the total number of spermatozoa counted and according to the number of subsamples taken from the original ejaculate, each subsample being used for making counts.
Exchanges of Sodium and Potassium in Mosquito Larvae
Authors: Ramsay J. A. 
Published: April 2021

ABSTRACT
The movements of sodium and potassium through the body and their exchanges between the body and the external medium have been studied in the larva of Aedes aegypti L. Briefly, both elements enter the body via the anal gills, are excreted by the Malpighian tubules and can be absorbed from the tubule fluid in the rectum. When either element is present in the medium to excess its concentration in the tubule fluid is increased and the extent of its absorption in the rectum is decreased. Under all conditions the concentration of potassium in the tubule fluid is greater than its concentration in the haemolymph, and the concentration of sodium is less. There is a circulation of potassium from haemolymph to tubule, to rectum or midgut and so back to haemolymph. The composition of the haemolymph in respect of sodium and potassium is remarkably constant in the face of changes in the medium. The volume of the larva appears to be regulated by a nervous mechanism. If the volume is increased peristaltic waves pass down the intestine more frequently and more fluid is voided through the anus.
A New Method of Measuring the Activity of Spermatozoa
Authors: Rothschild Lord 
Published: April 2021

ABSTRACT
A new and quantitative method of estimating the average speed of a suspension of spermatozoa has been developed. The method, in which the phenomenon known as probability-after-effect and kinetic theory principles are made use of, can be applied to any system of organisms which move in random directions, in one, two or three dimensions. The experimental procedure is to place a drop of sperm suspension on a microscope slide with a cover-slip on top of the drop, and photograph the spermatozoa at known time intervals. The number of spermatozoa in a region of known size is counted on each photograph. The estimated mean or average speed of the sperm suspension, , is given by the equation where r is the radius of a circular region in which the number of spermatozoa is counted, τ is the time interval between photographs, is the average of the square of the differences between the numbers of spermatozoa counted on consecutive photographs, and is the average number of spermatozoa in the circular region. Appropriate formulae for non-circular regions and for the precision of estimates of are given. A method of testing whether the directions of movement of spermatozoa are random has been applied to bull semen diluted 1/4 with phosphate buffer containing fructose. The movements were found to be random. The distribution of sperm speeds was determined and found to be somewhat skew and leptokurtic, with mean 123 µ/sec. and standard deviation 39. If dead or motionless spermatozoa were included, the mean speed became 117 µ/sec. Using the probability-after-effect equation given in (3), the mean speed of the suspension, including dead or motionless spermatozoa, was found to be in 111 µ/sec., with a standard error of 24·5. The standard error and therefore the precision of the estimate is under the control of the experimenter. Practical instructions for carrying out measurements are summarized in a separate section.
Observations on Certain Mechanical Properties of the Ligament of Pecten
Authors: Trueman E. R. 
Published: April 2021

ABSTRACT
The ligament of Pecten maximus consists of two layers, the outer extending along the dorsal margin of the valves, and the inner situated between the valves in the region of the umbo. The former appears fibrous and is somewhat similar to the outer layer of other ligaments. The inner layer consists of three parts, a large central noncalcified structure and two lateral calcified regions attaching the former to the valves. The central region is characteristic of the ligament of P. maximus and associated species, this layer being uniformly calcified in the ligament of most bivalves.
When the valves are closed the outer layer is subjected to tensile stress and the inner to compression, and the force so derived tends to open the valves. This force and that required just to close the shell are expressed as the opening and closing moments of the ligament respectively, and these have been determined for various lamellibranchs.
The exact conditions of the opening and closing of the valves have been observed by drawing the stress-strain curves for the intact ligament, plotting the applied moment against the angle of gape. The loading and unloading curves so produced describe a hysteresis loop. The area enclosed in that of Pecten (or Chlamys) is markedly less than that of other lamellibranchs and indicates the greater efficiency of the ligament of the former.
The mechanical properties of the isolated central region of the inner layer of the ligament of Pecten were investigated and showed similar properties to those of the intact ligament. The modulus of elasticity in compression of this region of the ligament of Pecten is approximately one-seventh of that of the inner layer of Ostrea or Lutraria, which are calcified structures. The ligament of the latter two bivalves has a greater opening moment but lower efficiency than that of Pecten. The characteristics of the ligament of Pecten are probably due to the central noncalcified region of the inner layer. The significance of these properties in regard to the swimming habit of Pecten is briefly discussed.
Central Nervous Function and Changes in Brain Metabolite Concentration
Authors: Chance M. R. A. 
Published: April 2021

ABSTRACT
The changes in the glycogen content of different parts of the brain have been studied in mice in relation to the behaviour of these animals. Increases in glycogen content have been demonstrated after a jump, a fall, after the righting reaction accompanying a fall, and after aggressive behaviour has been shown in a fight. No increase has been demonstrated during sleep, after running or walking, or after defensive behaviour in a fight. It was shown earlier that external stimulation must reach convulsive intensity to produce an increase in brain glycogen, and it is suggested that the particular forms of normal behaviour associated with increase in brain glycogen involve a ‘convulsive’ type of brain activity. ‘Convulsive’ in this context may mean either a disturbance of the metabolism in some or all of the brain cells, or alternatively the mobilization of cell populations for simultaneous, and probably rapid, discharge. At present there is no evidence to suggest whether either or both of these possibilities are involved.
Enzymic Oxidation of Amines in Decapods
Authors: Blaschko H. , Himms Jean M. 
Published: April 2021

ABSTRACT
Some time ago it was shown that a high concentration of the enzyme amine oxidase was present in the liver of Eusepia officinalis (Blaschko, 1941); it has since been found that this is also true for Octopus vulgaris (Blaschko & Hawkins, 1952a). In both species the enzyme occurs in other tissues as well as in the liver.
Studies on the Myoneural Physiology of Echinodermata
Authors: Pople Walter , Ewer D. W. 
Published: April 2021

ABSTRACT
A myoneural preparation of Cucumaria sykion (Lampert) comprising a pharyngeal muscle and the corresponding radial nerve is described. A brief account is given of the histology of the preparation. Direct stimulation of the muscle gives a single response. Above fusion frequency the tension developed by the muscle increases with increasing intensity of stimulation, but it is unaffected by the frequency of stimulation. Stimulation of the radial nerve elicits a double response from the muscle. There is a ‘quick’ response which shows no myoneural facilitation and a ‘delayed’ response which shows a well-marked and prolonged facilitation. The tensions developed by both quick and delayed responses depend upon the intensity of stimulation applied to the radial nerve. Both responses show well-marked refractoriness at stimulation frequencies above about 10 stim./sec. It is suggested that the delayed response arises from the activity of the internmcial neurones in the motor complex, and that this is also the locus of the prolonged facilitation shown by the delayed response. The similarity of the properties of this system with certain features of the chordate nervous system are pointed out, but it is considered that any simple phylogenetic conclusions are unwarranted."
The Physiology of Contractile Vacuoles
Authors: Kitching J. A. 
Published: April 2021

ABSTRACT
The contractile vacuole of the suctorian Discophrya piriformis Guilcher has been observed at hydrostatic pressures ranging up to 15,000 lb./sq.in. (1020 atm.). The rate of output of water was reduced at high pressures, and vacuolar activity was entirely suppressed at about 7000 lb./sq.in. (476 atm.). The vacuolar frequency was increased at 2000-3000 lb./sq.in. (136-204 atm.), but returned to normal on release of pressure. The frequency was depressed at 5000 lb./sq.in. (340 atm.) or more, but on release of pressure rose to a level higher than before treatment. The increase in vacuolar frequency at moderate pressures is perhaps comparable to the increase in tension of muscle at these pressures. High pressure probably promotes instability of the pore plug, and contraction and solation of the vacuolar wall.
The Mitotic Index and Interphase Processes
Authors: Walker P. M. B. 
Published: April 2021

ABSTRACT
The mitotic index of a cell population, defined by Champy as the per mille proportion of the population in any mitotic stage, has long been regarded as an important criterion of the growth and multiplication of tissues. It is commonly measured in fixed and stained specimens, and therefore represents the stage of the material at the time of fixing only. However, cells grown in tissue culture may be observed and photographed for a considerable period before any measurement is made; such observations, which have been reported elsewhere (Walker & Yates, 1952a, b), show that some cytochemical results may require reinterpretation.
The Absorption of Water by Woodlice
Authors: Spencer J. O. , Edney E. B. 
Published: April 2021

ABSTRACT
Experiments were undertaken to determine the site of water uptake, and the conditions in which it occurs, in Ligia oceanica, Oniscus asellus, Porcellio scaber and Armadillidium vulgare. Besides absorbing water with moist food, all four species were capable of active imbibition of water through both mouth and anus when a free water surface was available. In Ligia oceanica, imbibition occurred largely through the anus, in other species, through the mouth. Absorption through the anus was demonstrated by blocking the mouth by electro-cautery. All species save L. oceánica could imbibe water through the mouth from a damp surface (plaster of Paris) sufficiently rapidly to counteract the effect of transpiration from the integument in air at c. 85 % R.H. No water was absorbed through the anus in these conditions. The results help to resolve certain conflicting statements regarding the distribution of different species in the field. All species are for the most part ‘wet living ‘, but they differ as regards tolerance of suboptimal conditions.
A Note on the Pharmacology of the Dorsal Musculature of Peripatopsis
Authors: Ewer D. W. , Van Den Berg Roelof 
Published: April 2021

ABSTRACT
As far as they have been studied the muscles of the body wall of annelids have been found to be sensitive to acetylcholine. The dorsal musculature of Hirudo medicinalis L. responds by contraction to a low concentration of the drug (Minz, 1932); among the chaetopods a similar effect has been shown with the body wall of Lumbricus terrestris L., Arenicola marina L. (Wu, 1939) and Branchiomma vesiculosum (Montagu) (Nicol, 1952). In all cases the threshold of response is at dilutions of 10−4 to 10−6. No such responses have generally been found with the skeletal muscles of the Crustacea. Bacq (1935) reports that the muscles of Carcinus maenas (Pennant) and Lepas anatifera L. do not respond to acetylcholine at a concentration of 10-4; du Buy (1935) was unable to elicit any response to crystals of the drug from the muscles of Cambarus sp.; Katz (1936) found no response from the muscles of Carcinus maenas to acetylcholine at a concentration of 10-5, but observed a ‘moderate short contracture’ to a concentration of 10-4;* Ellis, Thienes & Wiersma (1942) detected no response from the claw muscles of Cambarus clarkii Girard even at concentrations of 10-1.