Outlines of chemico-hygiene and medicine, or the application of chemical results to the preservation of health, and cure of disease / by A. Dallas.

  • Dallas, A. (Angus)
Date:
1860
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of chemico-hygiene and medicine, or the application of chemical results to the preservation of health, and cure of disease / by A. Dallas. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    80 if examined separately, will exhibit with more minuteness still, the arrangement of the secreting machinery. The twig, coming from the branch a, of the artery, after entering the malpighian body B, separates into five, six, seven or eight branches; each of which divides again into a bunch of capillaries. It is from these capillaries, during the passage of the arterial blood through them, that the urine is secreted into the minute uriniferous ducts which con- verge and form the uriniferous tube L, L, which takes a winding course in the direction of the pelvis. Alongside of the afferent twig, the efferent vein F, is seen emerging. It convolutes and forms a plexus around the uriniferous tube, terminating in the renal vein V. With reference to the structure of the arte- ries and veins, which structure directs the course of the blood in the kidneys when they are compressed, it is necessary to remark that arteries have no valves; whereas the veins have. The reason of this arrangement is, that arterial blood, the blood which flows in the arteries, being pure and in composition the same as the oxidized blood issuing from the left division of the heart, produces no injurious effect, when it recedes in the arteries by regurgitation. On the other hand, venous blood, being in great part the refuse of the decomposed tissues, intended for expulsion from the system, could not flow back into the arteries without, at the same time, altering the condition of the arterial blood, and, accordingly, doing mischief. To prevent this, the veins are found to have valves, in all those parts, where they are required. These valves are so constructed, that they prevent the venous blood from going back into the arteries; and it is, therefore, forced to take a direct course onwards. In the capillaries and small veins, no valves are perceptible; but there is a provision which answers the same purpose. They possess longitudinal and projecting formations, called nuclei; some of which are placed transversely, in such positions as require that the absence of valves should be compensated by structures capable of serving the PLAN OF THE RENAL CIR- CULATION ; AFTER BOWMAN. a. Small branch of an artery. 1. Malpighian body. L L, Uriniferous duct. F, F. Efferent veins leading to V, tho large venal vein.