bluuebunny/crossref_metadata_2025 huggingface dataset:
Active Transport by the Cecropia Midgut
Authors: Haskell J. A. , Harvey W. R. , Clark R. M.
Published: April 2021

The electrical potential across the isolated midgut of five developmental stages of the Cecropia silkworm was studied by changing the concentration of single cations in solutions bathing each side of the midgut. The stages included feeding fourth-instar insects, insects moulting from the fourth to the fifth instar, feeding fifth-instar insects, insects which had evacuated their midguts, and insects spinning cocoons. Average values of the initial maximal potential exhibited by the midgut in solutions containing K, Mg, and Ca but no Na, for the stages mentioned above, were 68, 83, 90, 124, and 2 mV., respectively. In all of the developmental stages studied except the ‘spinning larva’, reducing the potassium concentration from 32 to 2 mM/l. on the blood-side of the isolated gut lowers the potential, on the lumen-side of the gut raises the potential and on both sides gives an intermediate value. When the potential prior to a decrease in concentration of potassium on the blood-side is over 100 mV., the Nernst slope approaches 59 mV. A tenfold reduction in the concentration of magnesium or the addition of 32 mM/l. sodium to the solutions bathing the isolated gut has no systematic effect on the potential. A tenfold drop in the concentration of calcium in the solutions causes changes in the potential in the opposite direction from those predicted by the Nernst equation. The pH of the midgut contents rises from early fourth instar to late fifth instar. The hydrogen-ion concentration of the blood is about 1000 times more than that of midgut contents in fifth-instar insects. Neither synthetic ecdysone, partially purified natural ecdysone nor juvenile hormone has an effect on the potential or current of the isolated midgut over periods as long as 30 min.
Visual Thresholds and Spectral Sensitivity of Herring Larvae
Authors: Blaxter J. H. S.
Published: April 2021

Herring larvae are characterized by eyes with no rods and no retinomotor responses, though both are present in the adult. By observing the extinction of phototactic behaviour and feeding in herring larvae of different ages held at low intensities of white and coloured light, it was possible to obtain a measure of both threshold light intensities and spectral sensitivity for a pure-cone eye. The phototaxis was positive at higher intensities, the threshold being 100 to 10−1 m.c. Below this threshold a negative phototaxis was observed which disappeared at a much lower threshold, about 10−5 to 10−6 m.c. The threshold for feeding varied with age and the type of food organism, lying between 10−1 and 10−2 m.c. The high sensitivity for negative phototaxis was probably a visual response and not one mediated by a dermal light sense. Spectral sensitivity varied depending on age and behavioural criteria. Using feeding and positive phototaxis the action spectrum was broad and plateau-like with a maximum in the yellow-green and would appear to be similar to other photopic curves. The action spectra for negative phototaxis showed a number of peaks. At hatching three peaks at 450, 520 and 600 mμ might represent three types of cone as postulated by the Young-Helmholtz theory of colour vision.
Respiratory Exchange and Evaporative Water Loss in the Flying Budgerigar
Authors: Tucker Vance A.
Published: April 2021

Oxygen consumption of 2 budgerigars (Melopsittacus undulatus) was measured during level, ascending and descending flights lasting 5–20 min. in a wind-tunnel at speeds between 19 and 48 km./hr. In level flight oxygen consumption was lowest at 35 km./hr. with a mean value of 21·9 ml. (g. hr.)−1 or 12·8 times the standard value calculated for these birds (weight = 35 g.). At a given speed oxygen consumption was highest for ascending flight and lowest for descending flight. Carbon dioxide production was measured on one bird flying level at 35 km./hr. for 20 min. The ratio of carbon dioxide production to oxygen consumption was 0·780, indicating that the bird was oxidizing primarily fat. The efficiencies of level, ascending and descending flight are discussed. The measurements indicate that for the budgerigar 42 km./hr. is the most economical speed for covering distance, and below 27 km./hr. undulating flight is more economical than flight at a constant altitude. Evaporative water loss in level flight was measured in two birds for 20 min. at 35 km./hr. at temperatures of 18–20° and 29–31° C. At 36–37° C. the birds became overheated and would not fly for as long as 20 min. Evaporative water loss at 18–20° C. was 20·4 mg. (g. hr.)−1. It increased to 63·9 mg. (g. hr.)−1 at 36–37° C. After accounting for metabolic water production and faecal water loss, budgerigars flying at 18–20° C. had a net water loss of 11 mg. (g. hr.)−1. At this temperature 15 % of the estimated heat production in flight was lost by evaporation of water, while 47% was lost by evaporation of water at 36–37° C. Lung ventilation, tidal volume and partial pressure of carbon dioxide in expired air were estimated for flying budgerigars from evaporative water-loss data. In level flight at 18–20° C and 35 km./hr. these quantities had values of 398 ml. (g. hr.)−1, 0·033 ml. (g. breath)−1 and 37 mm. Hg. respectively. Respiratory rate in level flight was measured in 2 birds at speeds between 19 and 48 km./hr. Respiratory rate depended on speed and was lowest at 35 km./hr. Since wing-beat frequency was constant at 840 beats/min. at all speeds, respiratory rate and wing-beat frequency were not synchronized. Published data and analysis of dimensional relations of birds suggest that in birds the size of a budgerigar or smaller a respiratory rate equal to the wing-beat frequency would be too high for efficient ventilation of the lungs. Birds the size of a pigeon or larger probably have synchronous wing beats and respirations.
Structure and Physiology of A Chordotonal Organ in the Locust Leg
Authors: Usherwood P. N. R. , Runion H. I. , Campbell J. I.
Published: April 2021

The structural and physiological properties of a chordotonal organ found in the metathoracic femoral segments of the locust and grasshopper are described. Recordings from the afferent fibres of this mechanoreceptor reveal two patterns of activity: a static or tonic discharge and a dynamic or phasic, rapidly adapting discharge. The frequency of the tonic discharge varies with the femur-tibia angle, while the phasic discharge occurs in response to angular movements of the tibia of > 3’. The frequency of the phasic response is related to the velocity of tibial displacement. The responses recorded during flexion of the tibia are different from those recorded during extension. Removal of either of the metathoracic chordotonal organs produces significant changes in walking and postural behaviour. Leg reflexes involving the femoral chordotonal organ and femoral muscles appear to play a very significant role during postural and walking activity.
Sodium Regulation and Adaptation to Fresh Water in Gammarid Crustaceans
Authors: Sutcliffe D. W.
Published: April 2021

Sodium uptake and loss rates are given for three gammarids acclimatized to media ranging from fresh water to undiluted sea water. In Gammarus zaddachi and G. tigrinus the sodium transporting system at the body surface is half-saturated at an external concentration of about 1 mM/l. and fully saturated at about 10 mM/l. sodium. In Marinogammarus finmarchicus the respective concentrations are six to ten times higher. M. finmarchicus is more permeable to water and salts than G. zaddachi and G. tigrinus. Estimated urine flow rates were equivalent to 6·5 % body weight/hr./ osmole gradient at 10° C. in M. finmarchicus and 2·8 % body weight/hr./osmole gradient in G. zaddachi. The permeability of the body surface to outward diffusion of sodium was four times higher in M. finmarchicus, but sodium losses across the body surface represent at least 50 % of the total losses in both M. finmarchicus and G. zaddachi. Calculations suggest that G. zaddachi produces urine slightly hypotonic to the blood when acclimatized to the range 20 % down to 2 % sea water. In fresh water the urine sodium concentration is reduced to a very low level. The process of adaptation to fresh water in gammarid crustaceans is illustrated with reference to a series of species from marine, brackish and freshwater habitats.
Effects of Sub-Lethal High Temperature on An Insect, Rhodnius prolixus (Stål.)
Authors: Okasha A. Y. K.
Published: April 2021

The effect on moulting of exposing 1st-, 2nd-, 3rd- and 4th-stage larvae of Rhodnius to 36.5° C. immediately after feeding was studied. After transfer to normal temperature (28° C.) moulting is delayed; the duration of the delay is directly proportional to the period of exposure to high temperature. Unfed larvae exposed to high temperature exhibit delayed moulting when placed at normal temperature after feeding, and prolonged exposure also inhibits micturition which normally occurs directly after feeding. Since the Malpighian tubules appear to function normally, it is suggested that the inhibition of the mechanisms responsible for emptying the rectum results in the cessation of micturition. The harmful effects on moulting of heat-treatment of unfed larvae can be eliminated by placing the exposed insects at normal temperature for an appropriate period before feeding. Exposure to high temperature either before or after feeding results in the decrease and malformation of the sensory bristles and plaques in the next larval stage.
Molecular Sieving of Hydrophilic Molecules by the Rectal Intima of the Desert Locust (Schistocerca gregaria)*
Authors: Phillips J. E. , Dockrill A. A.
Published: April 2021

The permeability of perfused intimal sacs to fourteen non-ionic, hydrophilic molecules of graded molecular size was estimated by radioisotope flux. The rectal cuticle acts as a molecular sieve severely restricting the rate of penetration of molecules with increasing hydrated size. The penetration of test molecules was as predicted by the Renkin equation for a uniform population of water-filled pores having radii of 6.5 Å. The properties of cuticles from the rectum and the integument are compared and the role of the rectal intima in the excretory process in the desert locust is discussed.
Recurrent Inhibition in the Giant-Fibre System of the Crayfish and its Effect on the Excitability of the Escape Response
Authors: Roberts Alan
Published: April 2021

A single impulse in any one of the central giant fibres of the crayfish is sufficient to evoke a full escape response. Following such a single impulse a search was made for inhibitory processes of similar duration to the driving movement of the escape response. There is no inhibition of flexor motoneurones or muscles to prevent response to impulses in the central giant axons during the escape response. However, following an impulse in any central giant, intracellular recording showed that there is inhibition of excitatory input to the lateral giants in the abdomen. This inhibition suppresses impulse generation for the duration of the escape response. The inhibition coincides with slow, depolarizing potentials in the lateral giants. These have an equilibrium potential between the normal resting potential and the threshold for spike initiation in the lateral giants. During these slow potentials there is a postsynaptic resistance decrease coinciding very closely in time course with the inhibition of excitatory input. The slow potentials are therefore identified as IPSPs (inhibitory postsynaptic potentials) because of their close association with a postsynaptic inhibitory process. This conclusion is endorsed : (a) by the absence of similar slow potentials in the abdominal medial giants which have no excitatory input at this location, and (b) by the diminution of the slow potentials by picrotoxin, a drug known to block inhibition at many crustacean synapses. When evoked repetitively, even at low frequencies like 0·25 per sec., the IPSPs decrease in amplitude. No other ‘after effects’ of repeated activity were found. Attempts to localize the inhibitory synapses are frustrated by the large space constant of the lateral giants. However, the evidence is compatible with the notion that inhibition originates within each abdominal ganglion. There is occlusion and crossed response decrement between the central giant axons evoking lateral giant inhibition. This suggests that the different presynaptic fibres excite some common inhibitory pathway in each ganglion. Further experiments showed that pathways producing inhibition in one ganglion can be excited in others. Interneuronal arrangements to explain properties of the inhibitory pathways are discussed. Two functions are suggested for the recurrent inhibition in the crayfish lateral giants. First, it may limit the number of impulses that are evoked by a single afferent excitatory volley. Secondly, it may coordinate successive escape responses by suppressing impulse generation in the lateral giants during such responses.
Aestivation and Ionic Regulation in Two Species of Pomacea (Gastropoda, Prosobranchia)*
Authors: Little Colin
Published: April 2021

The ionic composition of the haemolymph, and the concentrations of uric acid and protein, have been determined for the amphibious prosobranchs Pomacea lineata and P. depressa. Ionic composition of the haemolymph is similar to that of freshwater gastropods. The urine is decidedly hypo-osmotic to the haemolymph, reabsorption of ions occurring in the anterior chamber of the kidney. The rate of production of urine is approximately 1 μl./g./min. at 25° C. The onset of aestivation appears to be related to a loss of 20 % of the normal wet weight of the tissues. The loss of weight during aestivation averages 0·009 % of initial wet weight/hr., and aestivation may continue for over 400 days. During aestivation the osmotic pressure of the haemolymph may rise to twice its normal value; but this is 30 mM/l. NaCl less than that predicted from weight losses. The relative composition of the haemolymph alters little, except that the percentages of sodium and chloride increase. Uric acid accumulates round the blood vessels during aestivation, especially in the lung. Relatively little accumulates in the two chambers of the kidney, and only that in the posterior chamber is excreted later. Since the volume of fluid in the posterior chamber falls to about 10 % of its normal value, while the total loss of weight of the snail is about 50 %, the fluid in the posterior chamber acts as a water reserve. Recovery from aestivation occurs in about 24 hr., when the snails are placed in water. The posterior chamber of the kidney excretes high concentrations of uric acid during this time. The characteristics of aestivation are discussed, and compared with those shown by the Pulmonata.
Studies on Freshwater Osmoregulation in the Ammocoete Larva of Lampetra planeri (Bloch)
Authors: Morris R. , Bull J. M.
Published: April 2021

An investigation has been made of the factors which cause sodium loss from ammocoetes when they are immersed in de-ionized water at 1° and 10° C. Sodium influx ceases when animals are first immersed in de-ionized water, but can recommence when the animal loses sufficient sodium to the environment. The concentration of sodium required for influx to take place decreases with succeeding periods of immersion in de-ionized water at 10° C. and reaches minimum equilibrium concentrations as low as 0·005 mM-Na/l. Low temperature inhibits sodium influx and thus promotes net loss of sodium to de-ionized water. Low temperature also decreases the initial loss of sodium to de-ionized water and probably lowers the permeability of the external surfaces of the animal to ions. This effect is small compared with the inhibition of ion uptake so that the combined result is to increase the net loss of sodium from the animal. Since animals lose calcium to de-ionized water and show a decreased rate of sodium loss when calcium salts are added, it is believed that the high rates of sodium loss in de-ionized water are attributable to the effect of calcium on permeability. Lack of calcium may also explain why animals which have been depleted of sodium by low-temperature treatment take up sodium much faster at higher temperatures from dilute Ringer solutions than from pure sodium chloride solutions. When animals lose ions to de-ionized water at low temperature, sodium and chloride are lost from the extracellular space, whilst the muscle cells lose potassium. These ions are recovered into the extracellular space when animals are allowed to take up ions at 10° C. from diluted Ringer solution later.
An Application of the Constant-Field Theory to the Behaviour of Giant Neurones of the Snail,Helix aspersa
Authors: Moreton R. B.
Published: April 2021

The resting potentials of giant neurones in the abdominal ganglia of the snail, Helix aspersa, have been measured, and their dependence on the extracellular concentration of potassium ions has been investigated. The behaviour of the resting potentials differs considerably from that of a potassium electrode, as given by the Nemst equation. A modification of the equation derived from the ‘constant-field’ theory is described, which transforms the equation for the resting potential into a linear relationship ; it is found that the experimental results can be fitted quite well by this equation, for potassium concentrations up to 12 mM. This is taken as evidence that the relative permeabilities of the cell membrane to potassium and sodium ions are independent of the external potassium concentration over the range of concentrations used. By fitting ‘best straight lines’ to the experimental data, estimates can be obtained from the ‘constant-field’ equation of the intracellular potassium concentration, and the ratio of permeabilities of the cell membrane to sodium and potassium ions, PNa/PK-The average results from experiments on fifty-seven neurones are : the error in each case being one standard deviation, calculated from the spread of the results. The average intracellular potassium concentrations of snail neurones show a distinct seasonal variation, being highest in the spring and lowest in the autumn. These changes are accompanied by changes in the selectivity of the cell membranes, as characterized by the ratio of permeabilities to sodium and potassium ions, so that the resting potentials of the cells are comparatively little affected. The changes could be connected with changes in the pattern of activity of the animals.
The Control of Water Loss in Locusta Migratoria Migratorioides R. & F
Authors: Loveridge J. P.
Published: April 2021

The rate of water loss from the cuticle of Locusta is proportional to weight. The rate of water loss from the cuticle at 30° C., 0% R.H. is 5·63 ±0·67 mg./ locust/hr., giving a permeability of 0·022 mg./cm.2/mm. Hg/hr. The transition temperature at 46–48° C. is similar to that of Schistocerca (Beament, 1959) and probably indicates the existence of an oriented lipid monolayer in the epicuticle. At relative humidities of 0–50% the rate of water loss from whole locusts decreases with time. This phenomenon, which does not occur at 75% R.H., is partly due to the loss of adsorbed hydroscopic water during the initial period. A continuing apparent decrease in transpiration is shown to be a true permeability change. The relationship between saturation deficit and rate of water loss at 30° C. is curvilinear, falling away at high saturation deficits. This results in a saving of water amounting to 1·5–2·5 mg./locust/hr. at 25% R.H. and 2·7–4·0 mg./locust/hr. at 0% R.H. and will be biologically significant if not an artifact. The anomalous relationship between saturation deficit and rate of water loss is caused by the permeability change occurring at low R.H. Three theories which may account for these phenomena are discussed.
The Control of Water Loss in Locusta Migratoria Migratorioides R. & F
Authors: Loveridge J. P.
Published: April 2021

The rate of total transpiratory water loss from Locusta is proportional to weight and is not affected by activity within the limits possible in an enclosed box. A trend for proportionately less water to be lost at low humidity than at high humidity probably involves active measures to control water loss from the tracheal system. The saving of water is 5 mg./locust/hr. at 0% R.H., 30° C. Experiments involving exposure of locusts to CO2 of different concentrations show that little control over water loss is exerted by the spiracles except in so far as they may influence the type of ventilation. Hyperventilation, predominantly of the tidal type, doubles normal water loss. Between 42 and 45° C. the ventilatory rate increases enormously with concomitantly greater water loss. Locusts pre-treated in dry air show a 23% reduction in abdominal ventilatory rate and a 25% reduction in water loss over locusts pre-treated in moist air. Ventilatory movements of locusts under conditions of progressive desiccation show decreased rate and amplitude and an increased incidence of discontinuities, which will conserve water. Ventilation and water loss are closely interdependent. The fact that ventilation can be controlled according to water reserves and the humidity of the air is important in water conservation.
Further Observations On the Physiology of Salinity Adaptation in the Crab-Eating Frog (Rana Cancrivora)
Authors: Gordon Malcolm S. , Tucker Vance A.
Published: April 2021

Total rates of urea loss from adult euryhaline crab-eating frogs (Rana cancrivora) adapted to various environmental salinities between fresh water and 80% sea water increase as salinity increases above 40% sea water. Oxygen consumption is constant in rate in all salinities studied. The presence of urea in the Ringer solution bathing isolated pieces of skin of frogs adapted to 60% sea water increases both the electrical potential and the inwardly directed short-circuit current across the skin. In skeletal muscle cells addition of intracellular solutes maintains tissue hydration in the face of large increases in plasma osmotic concentration in high-salinity media. Changes in the intracellular urea and free amino acid concentrations are primarily responsible for increases in intracellular osmotic concentration. Some implications of these observations are discussed and comparisons made with the euryhaline green toad, Bufo viridis.
Tonic and Phasic Systems in Parallel in the Eyecup Responses of the Crab Carcinus
Authors: Horridge G. A. , Burrows M.
Published: April 2021

Static positions of the eyecup are maintained by control of the frequency of impulses to tonic muscle fibres. In addition, phasic muscle fibres are excited when an optokinetic stimulus containing frequency components faster than about 0·1 Hz. exceeds about 0·1° in amplitude. Within the above limit, components of the stimulus of greater frequency or amplitude excite the phasic system, which adapts in a few seconds. Normally the tonic and phasic systems act in parallel. With oscillatory movements of a striped drum the tonic and phasic units do not have the same phase relation to the stimulus. The numerous components in parallel are so varied and interact at all stages, so that they cannot be related quantitatively to an analysis of the overall response. Although changes in frequency at each movement are large in one muscle and small in another, there is no question of coarse and fine control because none are separately controlled or dependent on the eyecup position.
Eyecup Withdrawal in the Crab, Carcinus, and Its Interaction With the Optokinetic Response
Authors: Burrows M. , Horridge G. A.
Published: April 2021

Protective withdrawal of the eyecup is caused by a burst of impulses in two axons of the optic tract, one to muscles 19 a, 19 b and 20 a, the other to muscles 18, 20b, 21 and 22. At a reflex eyecup withdrawal other concurrent activity is mechanically overridden; the tonic activity in only one muscle is inhibited centrally. At a ‘spontaneous’ withdrawal, however, all motor activity to that eyecup is inhibited. The largest muscle, 19 a, inactive in other eyecup movements, is the prime mover in withdrawal, and some tonic fibres of this muscle hold the eyecup withdrawn. Two muscles which move the eyecup toward the mid line on optokinetic responses are excited during a withdrawal. It is therefore possible for one muscle to contribute to movements in opposite directions. Repeated reflex withdrawal of an eyecup moving towards the mid line inhibits the optokinetic response of the other eye. Weak stimulation of an eyecup region by a variety of means, including withdrawal, improves the optokinetic response of that eyecup and sometimes of the other eyecup
Observations On the Intake of Water and Electrolytes by the Duck (Anas Platyrhynchos) Maintained On Fresh Water and On Hypertonic Saline*
Authors: Fletcher G. L. , Holmes W. N.
Published: April 2021

Intake of food, water and electrolyte by ducks maintained on fresh water and on hypertonic saline were measured over periods up to several months. Transfer to saline approximately equivalent to 60% sea water was followed during the first 24 hr. by a sharp rise and fall in the plasma concentrations of sodium and chloride, which thereafter remained similar to the concentrations found in the freshwater-maintained birds. Transfer to saline equivalent to 100% sea water resulted in a rise in these concentrations during the first 10 hr., which continued for a period up to 14 days, after which the birds either died or became unhealthy. Upon transfer to saline drinking water (284 mM/1. Na+, 6·0 mM/1. K+) there was a gradual loss of body weight accompanied by a reduction in the food and water intake. Body weights tended to become stable after about 3 weeks, but some individuals continued to lose weight while others regained what they had lost. When the concentration of sodium chloride in the drinking water exceeded 143 mM/1. the amount of sodium chloride ingested remained constant. Thus there was progressive decline in the volume of water drunk as the concentration increased. It would appear therefore that the saline-adapted duck possessed some mechanism whereby the daily intake of sodium chloride was regulated. The cloacal output from saline-adapted ducks over a 24 hr. period showed that only 10% of the ingested sodium was excreted via this pathway as compared with over 70% of the ingested potassium. Most of the sodium appeared to be excreted via the nasal glands. The possible interactions between the renal and extra-renal excretory pathways in the maintenance of homeostasis during adaptation to diets including hypertonic saline or seawater are discussed.
Pharmacological Properties of Excitatory Neuromuscular Synapses in the Locust
Authors: Usherwood P. N. R. , Machili P.
Published: April 2021

The effects of a wide range of amino acids and related compounds on retractor unguis nerve-muscle preparations from the locust, grasshopper and cockroach have been investigated. L-glutamate is the most active excitatory substance. The presence of two acidic groups and one amino group is essential for excitatory activity while the position of the amino group is of some importance in determining the level of activity. When L-glutamate is applied iontophoretically to the muscle fibres, ‘glutamate’ depolarizations are recorded only at the synaptic sites. Other evidence that the action of glutamate is restricted to the synaptic sites is presented. Perfusion of isolated locust retractor unguis nerve-muscle preparations with locust haemolymph does not markedly affect the neurally evoked mechanical responses. It appears that locust haemolymph contains little ‘free’ L-glutamate. Four acidic amino aids have been identified in the perfusate from isolated retractor unguis preparations namely, glycine, alanine, aspartate and L-glutamate. However, only L-glutamate increases in concentration during stimulation of the retractor unguis nerve.
Electrical Activity in the Hydroid Cordylophora
Authors: Mackie G. O.
Published: April 2021

Cordylophora has two major hydranth pacemaker systems, one producing slow,, biphasic pulses at 2·0–4·0 sec. intervals (slow pulse or SP system) and one exhibiting sharp, predominantly negative potentials singly or in bursts with a normal interval of 1·5−2·0sec. between pulses (fast pulses, FPs). Both SPs and FPs are recorded throughout the hydranth, but do not spread to and are not co-ordinated in adjacent hydranths. SPs could not consistently be evoked artificially and showed no clear behavioural correlates. FPs occur during feeding and following electrical stimulation, where they may accompany a muscle response. FPs appear superimposed on SPs when both systems are active. Such a composite event advances the SP rhythm by an amount close to the normal FP inter-pulse time, but compensatory adjustment of the SP rhythm then occurs. Treatment with 10−5g./ml. tetrodotoxin has no apparent effect on Cordylophora.
Changes in Textural Preferences in Octopus After Lesions
Authors: Wells M. J. , Young J. Z.
Published: April 2021

Octopuses repeatedly tested at alternate trials with rough and smooth spheres presented without reward take more of the smooth than the rough spheres. The individuals that take most often show the greatest preference. The overall tendency to take decreases within each session of sixteen trials and recovers by the next session some hours later. There is a slight decrease in mean takes over the first few sessions but the level then remains at about 36% over ten sessions of sixteen trials. Animals without vertical lobes tested in the same way without rewards take more often (at 60% of all trials). As with the normals there is a decline in take within each session: Extinction is therefore not exclusively the result of changes in the vertical lobe. The preference for smooth is less marked in animals without the vertical lobes than in normals. Animals with the supraoesophageal lobes split by a vertical cut (‘half-brain animals ‘) and animals with the supraoesophageal lobes removed except for the buccal and ventral subfrontal take fewer objects than normal octopuses. The same animals show reduction or reversal of the smooth preference manifest in normal octopuses. Removal of the whole of the inferior frontal system produced animals that take more often than normal, at 63% of all trials. These octopuses showed a marked preference for smooth. The system for release of objects is defective in these animals and this may act to give the appearance of excesss of takes of smooth. The fact that blind but otherwise normal octopuses prefer smooth objects was confirmed in a discrimination training experiment. Normal animals trained with a smooth sphere as positive performed better initially than those trained in the other direction, though the asymptote reached was the same for both. Animals without vertical lobes showed in training about the same preference for smooth as normals but were variable. They learned more slowly than normals. Half-brain animals showed a strong preference for rough in training. The animals trained with smooth positive learned very slowly and had not reached the level of those trained with rough positive after 160 trials.
Respiration in the African Lungfish Protopterus Aethiopicus
Authors: Johansen Kjell , Lenfant Claude
Published: April 2021

Factors controlling aerial and aquatic breathing have been studied in the intact, free-swimming African lungfish, Protopterus aethiopicus. Frequencies of aerial and branchial breathing were correlated with gas tensions in the lung and in blood from pulmonary and systemic arteries and veins. Studies were made, on fish resting in aerated water, during exposure to air and during hypoxic and hypercarbic conditions in the environment. Both branchial and pulmonary breathing were irregular during rest in aerated water. The rate of branchial breathing normally exceeded that of air breathing. An increased rate and vigour of branchial breathing commonly preceded an air breath. There was no indication that a new air breath was related to the values of arterial Po2 Air exposure elicited a marked and immediate increase in the rate of air breathing. Hypoxic water never evoked any compensatory breathing responses while breathing from a hypoxic gas mixture quickly increased the rate of air breathing. Bubbling 5% CO2 in air into the aquarium caused a reduction in branchial breathing while the rate of air breathing increased. Nicotine injected intravenously or in the water close to the gills elicited an increase in both aerial and branchial breathing. Respiratory and circulatory events were correlated during undisturbed breathing and during artificial lung inflation. Increased cardiac output and a shift in regional blood flow to a higher pulmonary flow occurred with air breaths.
A Wind-Tunnel Study of Gliding Flight in the Pigeon Columba Livia
Authors: Pennycuick C. J.
Published: April 2021

A technique for training pigeons to fly in a tilting wind tunnel is described, and a method of determining lift and drag in gliding flight is explained. Drag measurements were made on wingless bodies and preserved feet in supplementary experiments. The results were used to analyse the measured total drag of live pigeons into (a) body drag, (b) foot drag, (c) induced drag, and (d) wing profile drag. As speed is increased, gliding pigeons drastically reduce their wing span, wing area and aspect ratio. The increased induced drag resulting from this is more than offset by a very large reduction in wing profile drag. Although the lift:drag ratio is at best 5·5-6·0, changes of wing area and shape keep it near its maximum, up to speeds at least twice the minimum gliding speed.
Power Requirements for Horizontal Flight in the Pigeon Columba Livia
Authors: Pennycuick C. J.
Published: April 2021

Certain measurements made on pigeons flying horizontally in a wind-tunnel are described. A method, based on helicopter theory, for calculating the power required to fly at any given speed is explained. Induced, profile and parasite power are calculated separately. It is concluded that the pigeon can fly horizontally without incurring an oxygen debt at speeds from 3 to 16 m./sec. The minimum power speed is 8 – 9 m./sec. The maximum continuous power output is estimated to be 10·5 W., and the corresponding oxygen consumption about 170 ml./min. The maximum (sprint) power is estimated to be 20·4 W., from observations of vertical climb after take-off. The estimated best lift: drag ratio in horizontal flight is 5·9, giving a range of 11·8 km./g. of fat oxidized for a 400 g. pigeon. It is argued from considerations of structural strength that the early part of the downstroke is used mainly to impart angular velocity to the wing, and that air loads are only developed after most of the angular acceleration has taken place. The tension in the pectoralis insertion may exceed 60% of the breaking tension in fast horizontal flight. The power calculation was repeated for the ruby-throated hummingbird, using published data. Estimated best range is about 900 km./g. of fat oxidized, achieved at 9 m./sec. The corresponding effective lift: drag ratio is 4 ·1. The variation of power required and power available with size is considered, and the effect on hovering and take-off performance of different birds deduced. Performance estimates for the pigeon and ruby-throated hummingbird are very poor by engineering standards, but consistent with these birds’ known abilities, and are in general agreement with estimates of effective lift: drag ratio derived from published data on other species.
Some Features of the Central Co-Ordination of A Fast Movement in the Crayfish*
Authors: Roberts Alan
Published: April 2021

The nervous and muscular activity pattern produced in an abdominal segment by a single giant-fibre impulse when all peripheral reflexes are abolished is described. This description depends on criteria for the identification of efferent neurones to the tail muscles. These are discussed and the identification of the inhibitor to the fast flexor muscles is established by anatomical homology. The pattern of response to a giant-fibre impulse is summarized in Fig. 4. Inhibition of the fast flexors, the lack of an extension command, the slow flexor contraction, the accessory neurone discharge and central nervous inhibition during the escape movement are among the features discussed.
The Energy-Sources in Ontogenesis
Authors: Needham Joseph
Published: April 2021

The percentage growth-rate curves for carbohydrate and protein in the chick enbryo have been determined and compared with those already in the literature for the percentage growth-rates of the whole embryo, the dry substance, the fat, and the calorific value. The composition of the embryo in gm. per cent, of dry weight has been calculated and an ontogenetic succession of carbohydrate, protein, and fat, has been brought to fight. These three cell-constituents are at their highest levels in the embryo at 4, 11 and 20 days of incubation respectively. This may be correlated with the succession of maximum intensities of combustion, which have the same order (about 5,8· 5 and about 18 days). By comparing the curves for absorption-intensity with those representing the constitution of the embryo, it has been possible to trace the passage of building-materials from the yolk and white into the embryo and to analyse still further the movements of the fat and carbohydrate fractions. The concentration of the carbohydrate and protein in the water of the embryonic body has been calculated and compared with a curve already in existence for fat. The curve for intensity of absorption of total foodstuff has been calculated from the results of chemical analyses. It agrees as well as can be expected at present with that calculated from the oxygen consumption and the increase of dry substance in the embryo. The ratio Carbohydrate : Protein decreases during development, thus falling into line with the ratios Water : Solid, Inorganic Substance : Organic Substance, and Protein : Fat. Certain speculations arising out of these facts are discussed. There is a relation of simultaneity between the combustion of carbohydrate, protein, and fat, and the part these types of molecule play in the constitution of the whole embryo.
Galvanotropic Reactions ofPolycelis nigrain Relation to Inherent Electrical Polarity
Authors: Robertson J. Armitage
Published: April 2021

It occurred to the author that it was possible that some relation might be found to exist between the reactions of animals to stimuli and their physiological polarity and symmetry relations. It was necessary to use as stimulus some form of energy that was both continuous in action and controlled in direction. Light, though much used in experiments on animal reactions, would here prove unsuitable because of the variable nature of the responses called forth, and because a number of conditions alter the sign of phototropic response. Electrical current was chosen, and, since Planarians are animals in which physiological polarity is known to exist, and on which much work has been done, Polycelis nigra was used as the subject of experiment.
The Effect on Plants of Radiations From A Quartz Mercury Vapour Lamp
Authors: Delf E. M. , Ritson K. , Westbrook A.
Published: April 2021

A number of plants grown in the full daylight of a greenhouse have been exposed daily to the radiations of an Ulviarc mercury vapour lamp for very short time intervals, varying from 10 minutes to 30 seconds in the different experiments. Stunting and other formal and formative effects were seen with intervals of 1 minute and upwards. Exposures of 30 seconds on seedlings of Trifolium six weeks old appear to have no stunting effect and a favourable after-effect. Exposures of 2 minutes given to plants of Voandzeia receiving natural illumination for 7 hours or 5 hours daily have a more serious effect than when given to a plant receiving a 12-hour day.
The Qualitative and Quantitative Effects of Food on the Growth of A Soil Amoeba (Hartmanella Hyalina)
Authors: Cutler D. Ward , Crump L. M.
Published: April 2021

Among the free-living protozoa, excluding those forms which contain chlorophyll, two types of nutrition are found, holozoic and saprozoic; in the soil commonwealth there is an ample food supply for the saprozoic forms without reference to the other members of the micro-organic population, but the holozoic species present a different problem, since in the great majority of cases their food consists of the bacteria or other smaller organisms which occur with them in the soil solution. The idea that a normally holozoic animal might be induced to become saprozoic arose with the introduction of a suitable pure-culture technique. Among the earlier workers Beijerinck (1896), Frosch (1897) and Tsujitani (1898) all obtained “pure mixed cultures” of amoebae, and record their failure to grow these except in the presence of bacteria or yeasts, though Tsujitani was able to grow his amoebae with bacteria killed by heating them to 65 ° or 70 ° C. ; later Mouton (1902) records that an amoeba, a form obtained from soil, would not grow except in the presence of living bacteria, and Oehler (1916, 1924), who has perhaps worked more in this field than any other observer, has experienced great difficulty in obtaining any protozoan growth in cultures which do not contain bacteria or yeasts, either dead or alive, though successful growth was obtained in the case of Colpoda by feeding the culture with ground-up fish or powdered egg albumen. It further appears from Oehler’s work that, while the holozoic ciliates and flagellates are practically omnivorous provided that the food is supplied to them alive and of a suitable size, the amoebae tend to be very much more fastidious in their acceptance of food. All these writers seem to have been impressed by the enormous amount of bacterial food that a successful culture of protozoa can consume, and a quantitative study of this problem by Cutler and Crump (1924) showed that in the case of Colpidium colpoda in pure mixed culture the reproductive rate varied from 0·0 to 5·3 in 24 hours according as the number of bacteria per individual ciliate varied from 250 to 1,024,000; similar results have been obtained by Vieweger (1923)1, (1924).
On the Tropisms of Some Freshwater Planarians
Authors: Carpenter Kathleen E.
Published: April 2021

The behaviour of Planarians belonging to a variety of species has been shown by a number of workers to depend largely upon the action of external stimuli—mechanical, chemical, light, heat, contact, etc.—inducing responses usually described as “tropisms,” which, while subject to some slight individual variation, remain on the whole constant in character for stimuli of the given degree of intensity. Observations have been made on reactions of this type in certain species occurring within the Aberystwyth district of Cardiganshire (Carpenter, 1926, 1927), with the special object of determining how far, if at all, such responses may assist in determining the peculiar ecological distribution of the species in question; the results seem worthy of a brief separate consideration, as they show that there may be considerable diversity of reaction between even closely allied species.
Studies on Calcium Metabolism
Authors: McIsaac P.
Published: April 2021

Since the appearance of the works of Weiske, Voit, Forster, and others of later years, numerous attempts have been made to determine the various factors involved in calcium metabolism. Patterson carried out feeding experiments on rabbits and on himself and found that even a dietary deficient in calcium induced no loss of calcium in the blood. Moreover, with a fixed diet the urinary calcium varied but slightly, the variations being parallel with total amounts of urine excreted. One of his conclusions was that the greater the volume of urine excreted the greater was the mass of salts eliminated.
Studies on Calcium Metabolism
Authors: McIsaac P.
Published: April 2021

Several years ago Reach (1912) made comparisons of the amount of calcium that could be recovered from ashing of the entire bodies of male and female white mice. He worked with normal and gonadectomised males and females and obtained higher percentages of CaO from both groups of females (1·283 normal, 1·275 ovariotomised), and lower percentages from both groups of males (1·180 and 1·005). Reach accordingly arrived at the conclusion that “here we have a secondary sexual character—the ♀♀ of these animals are richer in Ca than the ♂♂.” More recently Hammett (1923) working on the femur and humerus of rats earlier thyro-parathyroidectomised at a hundred days found the amount of Ca in the males unchanged but slightly less than normal in the females, thereby suggesting some difference in the calcium metabolism of the sexes. Riddle and Honeywell (1925) undertook the study of calcium metabolism in relation to sex in the pigeon. They worked on blood serum, employing the method of Kramer and Tisdall (1921), and obtained two determinations from each bird at intervals of ten days. They obtained a sex-dimorphism, the males as a group showing a lower and the females a higher Ca content. They state, however, that only on a basis of sex had they found a consistent grouping of values.
The Effect of A Temperature Gradient on the Early Development of the Frog
Authors: Dean I. L. , Shaw M. E. , Tazelaar M. A.
Published: April 2021

The present paper is an account of experiments carried out under the direction of Professor Julian S. Huxley, in April and May, 1927, in an attempt to amplify and extend similar experiments done by the latter in the spring of 1926 (Huxley, 1926). The object of these experiments was to ascertain what effects a steep apico-basal temperature gradient has on the developing frog’s egg. The present experiments were carried out on a larger scale, their range being widened to include the effects of both apico-basal and lateral temperature gradients on later embryonic stages. The apparatus was improved, making it possible to use a steeper temperature gradient and so obtain more striking results. Some of the results have been embodied in a general paper (Huxley, 1927).
The Effect of Egg-Secretions on the Activity of Spermatozoa
Authors: Gray J.
Published: April 2021

Egg-secretions increase the rate at which the spermatozoa of E. esculentus absorb oxygen by about 300 per cent. Similar secretions may exert little or no effect on the respiratory level of the spermatozoa of E. miliaris. This difference between the species corresponds to the difference visible in the effect of the secretions on the mechanical activity of the two types of sperm. In the presence of egg-secretions the respiratory activity remains constant at a high level for at least 1 hour, whereas in the absence of secretions the level falls to about 30 per cent, of its original value in the same period of time. This effect is observed in both E. esculentus and E. miliaris.
An Experimental Study on the Effect of Thyroxin Upon Sexual Differentiation in the Fowl
Authors: Greenwood A. W. , Chaudhuri A. C.
Published: April 2021

An attempt was made to determine in the developing fowl embryo whether injections of thyroxin into the incubating egg would lead to a modification of the processes of sexual differentiation. The injections into the air space were made during the 3rd day of incubation, that is, at a time before the differentiation of the gonads in the two sexes can be demonstrated. Of the 190 eggs injected with thyroxin, 39 embryos survived of which 12 were markedly affected, reduced size of embryos being regarded as an indication of a marked hyperthyroidism which has resulted in an increase in the metabolic rate. No effect on the processes of sexual differentiation in either sex was found. The effect of the injections was not apparent before the 1 ith day. It will be attempted in a further series of experiments to determine whether this is a specific reaction of the thyroxin or whether it is due to mechanical hindrances to the absorption of the thyroxin into the foetal circulation until a considerable time after the injection. These experiments can not at present lead to any definite conclusion as to the relation between increased metabolism and the processes of sexual differentiation.