Abstract
LONDON Royal Society, February 27. W. R. GRAHAM, Jun., H. D. KAY and N. R. MCINTOSH: (1) A convenient method for obtaining bovine arterial blood. W. R. GRAHAM, Jun., T. S. G. JONES and H. D. KAY: (2) The precursors in cow's blood of milk fat and other milk constituents. S. J. FOLLEY and P. WHITE: (3) The effect of thyroxine on milk secretion and on some blood constituents of the lactating cow. The processes taking place in the mammary gland during milk secretion in the dairy cow have hitherto been difficult to investigate because no satisfactory method has been known for obtaining arterial blood without serious disturbance to the animal. Such a method has now been devised, and consists in puncture of the internal iliac artery through the wall of the rectum. The method is relatively safe and more than 150 arterial punctures have been made with only one fatal casualty. The following findings have been made: (1) the fat of cow's milk is derived in the main from the non-phospholipin fatty acids of the blood; (2) the phosphorus compounds of the milk derive their phosphorus from the inorganic phosphate of the blood plasma, and not from the phosphoric esters or the phospholipins of the blood; (3) relatively large quantities (up to 30 per cent) of the blood sugar are removed from the blood on passage through the mammary gland; (4) the number of volumes of blood required to produce one volume of milk is of the same order whether calculated from the fatty acid changes, inorganic phosphate changes, or sugar changes between arterial and venous blood. A rapid circulation of blood—probably at the rate of 300–400 volumes for each volume of milk secreted?takes place through the mammary tissue. There is a suggestion that one of the factors controlling the quantity and quality of the milk secreted is the arterial blood sugar level. This can be raised and kept above the normal level in the cow by thyroid feeding or thyroxin administration. The effect of thyroxin administration on the volume and quality of milk secreted by the cow has been carefully examined and the results subjected to statistical treatment. Under proper conditions a considerable increase in milk volume and in milk fat percentage and also in the percentage of non-fatty solids in the milk occurs. L. E. BAYLISS, R. J. LYTHGOE and KATHERINE TANSLEY: Some new forms of visual purple found in sea fishes with a note on the visual cells of origin. A number of new forms of visual purple, which are found in sea-water fishes and which have maxima of absorption between 505 mjjt. and 545mpL, are described. The absorption curves were obtained by a null-point photo-electric spectro-photometer. The instrument is capable of giving accurate readings with 0-5 c.c. of solution, and with a light intensity which is not sufficient to bleach the visual purple. It was found that there are alterations in the form of the absorption curves as a result of ‘bleaching’ of the yellow substances in the control solution, also there may be changes in the curve when the visual purple is extracted with distilled water. A histological examination of the retinae was made on each of the species used. The variety of visual purple carried by a species cannot be related to the available data on the depth which that species normally frequents, to the ancestry of the species, or to the histology of the retina of origin.
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Societies and Academies. Nature 137, 414–416 (1936). https://doi.org/10.1038/137414b0
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DOI: https://doi.org/10.1038/137414b0