Abstract
LONDON. Royal Society, March 22.—L. T. Hogben and F. R. Winton: The pigmentary effector system. III.— Colour response in the hypophysectomised frog. After complete removal of the pituitary gland, the melanophores remain permanently contracted, even when the frogs are exposed to conditions which are optimum for darkening of the skin; they can be made to expand by pituitary extract, but the animals regain pallor under conditions which invariably produce darkening in the normal or partially hypophysectomised (anterior lobe alone) frog. The minimum dose of pituitary extract for melanophore expansion was compared in normal and pituitaryless frogs. The experiments provide evidence that: (i) the rhythm of colour change in normal life is correlated with fluctuating amounts of pituitary secretion, and (2) direct nervous influences do not play a significant rôle in co-ordinating pigmentary responses in Amphibia.—H. R. Hewer: Studies on amphibian colour change. The presence of “frayed” ends to processes and isolated granules and irregular edges to the concentrated mass of granules precludes any theories postulating amosboid movement of cell processes. This is supported by (1) irregular movements of the granules; (2) slight massing of granules towards tips of processes in dispersed phase; and (3) stained sections of skin. Adult Rana temporaria respond, similarly to other Amphibia, to factors of normal environment. Dryness and light background cause concentration; moisture and dark background dispersion. Low temperature causes dispersion and medium temperature concentration. Higher temperatures appear to have an intermediate effect. Neither nitrogen nor hydrogen produced any effect during three hours; carbon dioxide did not affect colour before proving toxic; oxygen produced concentration in melanophores; chlorine changes melanin granules to a red colour.—J. Walton: On Rhexoxylon, Bancroft: a Triassic genus of plants exhibiting a liane-type of vascular organisation. The genus Rhexoxylon was instituted in 1913 for a fossil stem from South Africa. The evidence given by certain structural details was in favour of attributing it to the Palæozoic group of polystelic arborescent plants, the Medulloseæ. The study of additional specimens from South Africa shows that the organisation of the vascular system resembles very closely that of certain modern South American Lianes, especially in the anomalous methods of secondary thickening of the axis. Histologically, the secondary wood of Rhexoxylon resembles that of the group Dadoxyla, characteristic of the southern botanical province during the latter part of the Palasozoic era. Possibly Rhexoxylon, as a specialised ecological type, bore much the same relation to the gymnospermic Dadoxylon stock as the modern Liane bears to the angiospermic group at the present day, and the occurrence of an anomalous type of vascular system, in the modern Liane is an example of a repetition, in a distinct phylum, of a specialised organisation evolved in Palasozoic times. The fossil stem Antarcticaxylon priestleyi Seward, from South Victoria Land, Antarctica, has some of these peculiarities, and its occurrence in the Beacon Sandstone Series of Antarctica points to a probably close relationship between portions of this series and the Stormberg Series of South Africa, from which came the majority of specimens of Rhexoxylon.—G. Hewett: The Dusuns of British North Borneo. The Dusuns themselves claim descent from the Chinese who settled in North Borneo. The general political conditions in Asia during the thirteenth century led to the invasion of North Borneo by Kublai Khan. The Bruni tribute was transferred from Maiapahit to China, and the Chinese acquired the throne of Bruni. The Bruni government based its claim to the whole territory of North Borneo on the marriage of Sultan Akhmed to the Chinese daughter of Ong Shin Ping, who was in all probability the occupant of the Bruni throne at the time. The Chinese occupation and development probably lasted some four hundred years.—M. Tribe: The development of the hepatic venous system and the postcaval vein in the Marsupialia. The development of the hepatic veins is subject to variation. Two venous rings of vitelline origin are transformed into a spiral vessel encircling the gut. In most genera the left allantoic vein becomes the more important and in some genera it anastomoses with the spiral vessel. The mesenteric vein is probably derived, in part, from the caudal venous ring. The postcaval is derived from three sources. The postrenal section takes origin from the paired supracardinal plexus, the renal section from the subcardinal veins, the hepatic and prehepatic sections from the vitelline veins. The azygos and lumbar veins, and the suprarenal sinusoids, are derived from the supracardinal plexus. The left suprarenal vein is the persistent left subcardinal vein.—J. Gray: The mechanism of ciliary movement. III.—The effect of temperature. Between 0° and 33° C. the speed of the cilia on the gills of Mytilus increases with a rise in temperature, although the amplitude remains normal. Between 34° and 40° C. there is a marked falling off in the amplitude of the beat, followed by a reduction in speed. At 40° C. the cilia come to rest in the relaxed position. At 45° C. the cilia occupy the contracted position. The temperature coefficient of movement between 0° and 32.5° C. varies from 3.1–1.92. High temperatures have a destructive effect on individual cells of the epithelium. In well aerated tissue the oxygen consumption is directly proportional to the speed of the beat between 0°–30° C. At about 30° C. the initial oxygen consumption is not maintained, due to the dis-integrative effect of the temperature on the epithelium. The effect of temperature on the activity of cilia is closely parallel to its effect on cardiac muscle.—E. Ponder: The inhibitory effect of blood serum on hæmolysis. The hasmolytic action of saponin is inhibited by the proteins of serum, and also, to a lesser extent, by the cholesterol. The action of the bile salts is inhibited by the proteins, and by the lecithin of the serum. The inhibitory power is fairly constant in man and animals, is altered by drying the serum, and is affected by bacterial action. A quantitative study of the inhibition produced by serum shows inhibition is probably due to the formation of a loose compound between the proteins of the serum and the hasmolytic agent. The inhibitory effect of haemoglobin on hasmolysis produced by saponin and bile salts is considered. Probably the reaction which takes place between saponin or bile salts and red cells is a chemical one of the first order.
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Societies and Academies. Nature 111, 450–452 (1923). https://doi.org/10.1038/111450a0
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DOI: https://doi.org/10.1038/111450a0