. Elements of human physiology. Physiology. FUNCTIONS OF THE KIDNEYS AND SKIN 459 a clean experiment. In the first place the small veins of the kidney run alongside of the tubules and when dilated under the influence of venous congestion may press upon the latter, occluding their lumen and so stopping the flow mechanically. Moreover ligature of the renal vein cannot be regarded as equivalent to obstruction of the eft'erent vessels of the glome- ruli. It will be remembered that there is a very great difference as regards the effects on the intestmes between ligature of the portal vein and obstr
. Elements of human physiology. Physiology. FUNCTIONS OF THE KIDNEYS AND SKIN 459 a clean experiment. In the first place the small veins of the kidney run alongside of the tubules and when dilated under the influence of venous congestion may press upon the latter, occluding their lumen and so stopping the flow mechanically. Moreover ligature of the renal vein cannot be regarded as equivalent to obstruction of the eft'erent vessels of the glome- ruli. It will be remembered that there is a very great difference as regards the effects on the intestmes between ligature of the portal vein and obstruction of the inferior vena cava above the liver. It is impossible to inject the glomerular capillaries either through the renal portal capil- FiG. Bowman's C .>. p s u I e Diagram (after Morat) to illustrate the effect of active changes in the vasa afferentia and etferentia on the pressure in the glomerular capillaries. If the vas afferens constricts, the pressure will be represented by the lower dotted line. On the other hand, constriction of the vas efferens would raise the pressure in the glomerulus till it almost equalled that in the renal artery, as is shown by the upper dotted line. A, arteries; G, glomerular capillaries ; C, tubular capillaries ; V. vein. laries in the frog or through the renal vein in the mammal, and in view of the presence of well-developed muscular fibres in the vasa afferentia, we have no proof that any given rise of pressure produced in the venous side of the tubular capil- laries is transmitted effectively to the glomerular capillaries. It is a common experience to find, in injecting a kidney shortly after the death of the animal, that it is impossible to get any of the injection into the glomerular capillaries, although the injection may flow freely through all the vessels of the medulla. The diagram (Fig. 216) will serve to demonstrate the. Please note that these images are extracted from scanned page images that may have been digitally
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