bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Size and Swimming Speed on Locomotor Kinematics of Rainbow Trout
Authors: Webb P. W. , Kostecki P. T. , Stevens E. Don 
Published: April 2021

ABSTRACT
During swimming at constant speed the frequency (f), amplitude (a) and depth (d) of the tail trailing edge, and the length of the propulsive wave (λ) were measured for rainbow trout ranging in total length (L) from 5·5 to 56·0 cm. Fish were tested in a water flume using increasing velocity tests to sample a range of swimming speeds, V. λ was independent of V and related to size by: so that wavelength was relatively larger in smaller fish. 3.f was related to L and V according to: a was independent of V but was relatively smaller in larger fish: d was also independent of V but relatively larger in larger fish: Thrust power (= drag power) calculated using Lighthill’s small amplitude bulk momentum model was two to three times the theoretical minimum of a flat plate of equivalent length and area moving parallel to the flow with a presumed turbulent boundary layer. Froude efficiency increased with swimming speed, and it is shown that this is the usual relationship for fish studied so far. Froude efficiency was essentially independent of size at the critical swimming speed. Estimated aerobic efficiency increased with size at the critical swimming speed, implying that muscle efficiency also increases with size.
Distribution of Flow and Plasma Skimming In Isolated Perfused Gills of Three Teleosts
Authors: Olson K. R. 
Published: April 2021

ABSTRACT
Distribution of flow and red cells between the efferent (epibranchial) and venous pathways was examined with an isolated perfused gill adapted to collect the two effluents separately. Gills from two fish species (Ictalurids) with abundant prelamellar arteriovenous anastomoses (AVAs) were compared with those of the trout which contain few AV As. The gills were perfused with Ringer or Ringer containing 51Cr-tagged red cells (blood).
In Ringer-perfused gills, efferent outflow decreased as efferent pressure increased. Epinephrine prevented the decrease in efferent flow at elevated efferent pressures. In all species around one-third of the control blood perfusing the gill drained via the venous pathway. At constant efferent pressure epinephrine increased and acetylcholine decreased efferent outflow. These results suggest that tonic adrenergic stimulation is necessary for normal branchial perfusion.
The haematocrit of efferent effluent was greater than venous effluent in all species. No consistent effects of epinephrine or acetylcholine on plasma skimming were observed. Comparison of measured microhaematocrit and haematocrit values calculated from 51Cr red cell space suggests that the red cells in the venous effluent are larger than those from the efferent pathway and supports the concept of a nutritive function for the venous pathway.
On the Excitation of Crustacean Muscle. I
Authors: Pantin C. F. A. 
Published: April 2021

ABSTRACT
A brief account is given of the present position of the problem of neuro-muscular action in the Crustacea. A method is described by which the leg of Carcinus maenas may be perfused and stimulated. By this method the muscle remains in good condition for some 8 hours. By stimulating the nerve in Carcinus leg with alternating currents of increasing intensity a series of varied responses is obtained. Above the threshold a contraction is developed of a comparatively slow type. With increase of intensity of the stimulus the response fails, owing to the excitation of inhibitory nerves. But at still greater intensities contraction reappears. This contraction, however, is very rapid. Tetani developed from the slow contraction are easily inhibited. Tetani developed from the rapid contraction cannot be inhibited by superimposed stimuli. The relation of the quick and slow contractions is considered. It is not possible to fatigue one without fatiguing the other. Experiments show that on suddenly releasing the tension of the muscle during a tetanus, the tension always redevelops in a manner similar to the development of tension in the quick contraction, even though the tetanus be developed initially by the slow contraction. The same contractile mechanism is involved in both cases. The latent period of contraction on stimulation of the nerve is very long, and ranges from 300σ at the threshold. That for direct stimulation of the muscle is 7–10σ. Above the threshold the latent period shortens rapidly with increasing stimulus. Over this region the contractions are of the slow type. The latent period becomes asymptotic to 50σ as the intensity is increased. At this value the contractions are of the quick type. Inhibition is effective where the latent period begins to approach its asymptotic value. It is suggested that all the varied phenomena observed are related to the power of summation of crustacean muscle ; that the slow contraction in response to a battery of stimuli is not due to a different contractile mechanism from the quick one, but that it is a summation effect by which a statistically increasing number of muscle fibres are brought into action as successive impulses pass down the nerve.
The Osmotic Pressure of the Colloids in Fish Sera
Authors: Keys Ancel , Hill R. M. 
Published: April 2021

ABSTRACT
Measurements of colloid osmotic pressure and refractive index of five species of teleost fishes are recorded. A number of observations were made on eels which had been starved for two months. With the exception of the eel, the colloid osmotic pressures were less than half the characteristic level for mammals, the average being about 100 mm. H2O. Normal eels showed serum colloid osmotic pressures within the mammalian range, the starved eels showed values less than half as great but showed no signs of oedema.
A comparative table of colloid osmotic pressures for the vertebrates studied so far is presented.
The relation between refractive index and the colloid osmotic pressure is discussed briefly.
Some Effects of Fasting on the Composition of the Blood and Respiratory Exchange in Fowls
Authors: Henry Kathleen M. , Magee H. E. , Reid E. 
Published: April 2021

ABSTRACT
It has been shown that the blood sugar in the adult fowl, male or female, after falling during the first 2 days of fasting, rises on the 3rd or 4th day and then declines rapidly so that a well-defined peak is formed (Henry, Macdonald and Magee, 1933). This change was so constant in its occurrence that experiments were undertaken in the hope of throwing light on the immediate cause. As all the original glycogen stores are almost certainly exhausted after fasting for 3 or 4 days, the increase in blood sugar could only have come from protein or fat. A study was therefore made in fasting fowls of the uric acid and non-protein nitrogen contents of the blood, in the hope that, if any marked change in the metabolism of protein occurred, it would be reflected in alterations in the amounts of these present in the blood. In regard to fat the metabolites chosen were cholesterol and lecithin. The significance of these substances in fat metabolism is not very clear at present; but, as they can be readily and accurately estimated in small amounts of blood, they were preferred to blood fat as possible indicators of change in fat metabolism. The liver and muscle glycogen of fowls killed after different periods of fasting were also determined, as well as the effect of fasting on the respiratory exchange. Marked qualitative alterations in energy metabolism would, it was thought, be associated with corresponding changes in the R.Q. None of these lines of study threw any direct light on the problem we set out to solve ; but the results obtained were considered to be of sufficient interest in themselves to merit publication.
Cellular Transfer of Substances, Especially Neurohumors
Authors: Parker G. H. 
Published: April 2021

ABSTRACTThe dark longitudinal stripe (expanded melanophores) produced in the tail of Fundulus by a transverse denervating cut of 1 mm. length appears about half a minute after the cut is made, it reaches its maximum development in about an hour, and fades to the lightness (contracted melanophores) of the ordinary light fish in from 22 to 96 hours (average 29·7 hours). A dark longitudinal stripe similar to that described in paragraph 1, but from a 2 mm. cut, fades after 43–143 hours (average 78·3 hours). Light-tinted fishes, such as are noted in paragraphs 1 and 2, when put on a dark background, become fully dark, except for the stripe on the tail, in about 1·8 hours. Under such circumstances a 1 mm. stripe becomes dark within 17–27 hours (average 20·5 hours) and a 2 mm. stripe within 23–70 hours (average 37·4 hours). Dark-tinted fishes, when put on a light background, become fully light, except for the stripe on the tail, in about 4-6 hours. Under such circumstances, a 1 mm. stripe becomes light within 18–31 hours (average 26·4 hours) and a 2 mm. stripe becomes fight within 22–86 hours (average 51·6 hours). The darkening of the stripe (expansion of melanophores) and the fading of the stripe (contraction of melanophores) cannot be due to the nerves of the stripe, for these have been cut. The changes in colour are due to the gradual passage of an expanding neurohumor or of a contracting neurohumor from the adjacent regions into the stripe. This gradual change is much too slow for blood or lymph. It is believed to be due to a cell-to-cell transfer. Transfer of substances from cell to cell has been observed in plants (Kok), occurs in coelenterates, and is seen very probably in a number of instances in the human skin (spread of inflammation from radiated areas, erysipeloids, insect stings, and possibly vitiligo). Cell-to-cell transmission is a relatively slow process. Phylogenetically, it antedates transmission by blood and lymph.
Light Penetration Into Fresh Water
Authors: Pearsall W. H. , Ullyott Philip 
Published: April 2021

ABSTRACT
In the last paper of this series (Pearsall and Hewitt, 1933) changes in the transparency of the water of Windermere were described. It was shown that the penetration of blue light (5100 Å to 4000 Å), as measured by the sulphuric acidiodide method, was very much greater in 1920 than it was in 1932. The present communication deals with the results of observations on changes in the transparency of the water of Windermere throughout the year March, 1932, to March, 1933. The causes of the differences in the light penetration at different times of the year are discussed.
The Fertilisation of Rabbit Ova in Relation to Time
Authors: Hammond John 
Published: April 2021

ABSTRACT
By matings with fertile bucks at different intervals of time after a mating with a vasectomised buck (to induce ovulation) the time of insemination in the rabbit can be moved successively nearer to, at, and after the time of ovulation. From inseminations 5 hours before to 2 hours after ovulation the percentage of matings which are fertile, the average litter size, and average number of young per mating fall gradually and at a constant rate until absolute sterility is obtained. Does which produce large litters when mated normally (10 hours before ovulation) may be made to produce small litters by mating shortly before or after the time of ovulation. The ova are only capable of fertilisation while they are in, or as they leave, the plug at the top of the Fallopian tubes, i.e. up to about 6 hours after ovulation. They are incapable of fertilisation as they begin to move down the tube and acquire a layer of albumen around them. As a result of a mating made about the time of ovulation the apex of the “sperm swarm” arrives at the top of the tube in time to fertilise only those ova which still remain in the plug. The apex of the “sperm swarm” contains relatively few spermatozoa, and so small litters are produced. By “double matings,” of dominant and recessive coloured bucks on recessive coloured does, with a time interval between them, it is possible to measure the relative sizes of the “sperm swarms “at the tops of the tubes at different intervals of time after mating. The size of the “sperm swarm,” and so the interval of time over which it is possible to obtain fertilisation as a result of mating later than normal in relation to the time of ovulation, varies considerably in different males, The speed at which the sperms ascend the female tract is apparently not affected by the presence in them of male and female sex-determining elements. The duration of pregnancy is prolonged by reducing the size of the litter. With the prolongation of pregnancy the proportion of young born dead increases. Various possible causes for these facts are discussed. While there is but little constant increase in the weight of the individual young due to the prolongation of pregnancy from 31 to 34 days, there is a large increase in the individual weight due to reduction in the number of young in the litter. It is probable that the size of individual young is limited by the amount of some internal secretion or metabolic product of the mother.
Observations on the Fatty Constituents of Marine Plankton
Authors: Gunther E. R. 
Published: April 2021

ABSTRACTCollections of phyto- and zooplankton made off the Isle of Man were examined for vitamin content, and for chemical and biological characteristics. The important species entering into the composition of the plankton are noted, and a new method of estimating plankton catches is described. Figures which represent the numbers of a species present in a given quantity of plankton are translated into figures representing the volume occupied by that species. Comparisons are drawn between the numerical and volumetric estimations of the various zooplankton species. The phytoplankton catches taken in May showed a fairly uniform composition throughout the collecting period, species of the genera Chaetoceros and Lauderia forming more than 90 per cent, of the material. The zooplankton taken in July consisted mainly of Copepoda. The catches were of two types : those having a higher percentage of Acartia, Calanus copepodid stages IV and III, and the Peridinian Ceratium ; and those containing less of these but rich in the adult and other stages of Calanus finmarchicus. By the use of curves correlating length and volume, measurements of important species are translated into factors representing numbers per c.c.; application of these factors converts the numerical estimation of a species into an estimation in terms of volume. The numerical and volumetric estimations of various species in four separate groups of plankton are compared and the yield of oil from each group is also recorded. The volumetric method conveys a significantly different picture of the plankton than is to be gained from the numerical method alone. Calanus finmarchicus is shown to constitute a relatively larger part of the plankton than other more numerous but smaller species and likewise its adult or sub-adult stages than its earliest copepodid stages. The correspondence of a good oil yield with those groups having a high Calanus content is held to be suggestive of a possible correlation between the two. Chemical and biochemical analyses of planktonic organisms by other investigators are reviewed and their results compared with those obtained during the present work. The rôle of plankton organisms in the nutrition of various other organisms is discussed.
Experiments on Embryonic Induction
Authors: Waddington C.H 
Published: April 2021

ABSTRACT
The experiments to be described in this section were begun in October, 1931, but no successful experiments were performed until the end of 1932. A short note on the results obtained was published in Nature (Waddington, 1933 b). In the meantime, Bautzmann, Holtfreter, Spemann and Mangold (1932) had shown that in the Amphibia coagulated organisers are still able to exert the inductive capacities which they possess in the living state. This work followed on the earlier experiments of Marx (1931) who obtained inductions with narcotised organisers, and Spemann (1931 a) who found that the inductive capacity is retained when the organiser tissue is subjected to crushing. The same type of investigation into the nature of the inducing agent in the amphibian organiser has now been carried still further by Spemann, Fischer & Wehmeier (1933), Holtfreter (1933 a and b) and Waddington, Needham & Needham (1933 a and b), all of whom have prepared cell-free organising extracts. The last-named authors have been able to show that the active substance is ether-soluble, but Fischer & Wehmeier (1933) claim that the substance is glycogen.
The Relations Between Yolk and White in the Hen’s Egg
Authors: Smith A. J. M. 
Published: April 2021

ABSTRACT
The white of the hen’s egg is in equilibrium with ice at a temperature of approximately − 0·45° C., the yolk, according to most observers, at approximately − 0·58° C. More surprising than the mere existence of such a difference in the newly formed egg is the fact that this difference seems to persist, although to a gradually decreasing extent, in eggs preserved for a considerable period. The phenomenon may be of biological significance in the fertile egg, in connection with the passage of water yolkwards during incubation.
Metabolic Changes Associated With Endo-Crine Activity and the Reproductive Cycle in Xenopus Laevis
Authors: Shapiro H. A. , Zwarenstein H. 
Published: April 2021

ABSTRACT
Experiments are described which show that active extracts of ovarian tissue minus corpus luteum can be obtained which significantly raise the lowered level of the serum calcium in ovariectomised toads ; and also raise the serum calcium level in normal toads above the normal level. Injection of adequate doses of antuitrin (Parke, Davis and Co.), raises the lowered level of serum calcium in hypophysectomised toads almost to normal ; and of ovariectomised toads to the normal level. The effect is obtained more readily in the ovariectomised condition. Injection of pituitrin (Parke, Davis and Co.), depresses the serum calcium level in normal, ovariectomised and completely hypophysectomised toads. The effect is more readily obtained in the normal intact animal than in the ovariectomised or the totally hypophysectomised state, when the ovaries have undergone involution. It is suggested that there is evidence that the principles exerting a hormone-like action on calcium metabolism are not, in the case of the ovary, either oestrin or the luteal hormone, or in the case of the pituitary, the gonadotropic hormone.
Some Observations on the Respiration of Certain Tropical Fresh-Water Fishes
Authors: Willmer E. N. 
Published: April 2021

ABSTRACTThe blood of the fish of the rivers and swamps of British Guiana is not all equally affected by CO2. A regular series can be shown to exist between the paku (Myleus setiger Müll and Troschel), an active river fish whose blood is considerably affected, and the electric eel (Electrophorus electricus (L.)), which is an air-breather, frequenting relatively stagnant and poorly oxygenated water, and whose blood is almost independent of the presence of CO2. The blood of all the fish examined was found to be acid, generally about pH 6·7. The CO2 combining power of the blood of the fish examined was found to be very much lower than in other animals, but higher than might be expected on theoretical grounds. The possibility of another type of buffering is suggested. In the one fish examined (the bom-bom, Pterodorasgranulosus (Vai.)) the CO2 contained in reduced blood was found to be no higher than in oxygenated blood. In spite of the low oxygen content of some of the waters, no fish examined showed a haemoglobin with any markedly increased affinity for oxygen, such as might enable it to be saturated more easily at low pressures. The yarrow (Erythrinus erythrinus (Schn.) or Hoplerythrinus unitaeniatus (Spix.)) was found to be a fish which could either use its gills or take in bubbles of air into its air-bladder as a means of respiration. This fish has been studied in detail and the conditions controlling its respiration are described. Three factors are concerned, pH, oxygen content of the water, and CO2 content of the water. Of the three the last is most often the limiting factor. Carbonic anhydrase was found in the blood of all the fish examined for its presence, which include practically all those mentioned in this paper. The bearing of these results on certain problems of general biological interest is discussed.
Brain Oscillator(s) Underlying Rhythmic Cerebral And Buccal Motor Output In The Mollusc,Pleurobranchae Calieornica
Authors: Davis W. J. , Kovac Mark P. , Croll Roger P. , Matera Eugene M. 
Published: April 2021

ABSTRACTTonic (d.c.) intracellular depolarization of the previously identified phasic paracerebral feeding command interneurones (PCps) in the brain of the carnivorous gastropod Pleurobranchaea causes oscillatory neural activity in the brain, both before and after transecting the cerebrobuccal connectives. Therefore, cycle-by-cycle ascending input from the buccal ganglion is not essential to cyclic brain activity. Instead the brain contains an independent neural oscillator(s), in addition to the oscillator(s) demonstrated previously in the buccal ganglion (Davis et al. 1973). Transection of the cerebrobuccal connectives immediately reduces the previously demonstrated (Kovac, Davis, Matera & Croll, 1983) long-latency polysynaptic excitation of the PCps by the polysynaptic excitors (PSEs) of the PCps. Therefore polysynaptic excitation of the PCps by the PSEs is mediated by an ascending neurone(s) from the buccal ganglion. The capacity of feeding command interneurones to induce neural oscillation in the isolated brain declines to near zero within 1 h after transection of the cerebrobuccal connectives, suggesting that this capacity is normally maintained by ascending information from the buccal ganglion. The results show that this motor system conforms to a widely applicable general model of the neural control of rhythmic behaviour, by which independent neural oscillators distributed widely in the central nervous system are coupled together to produce coordinated movement.