_Salivation_ and _myosis_, as well as diarrhea, are often noticed in so-called _uremia_. In that form known as hepatic uremia, when the liver no longer forms urea, the kidneys scarcely act. In other words, if urea is no longer present in the body, the kidneys are deprived of their principal stimulation to physiological activity. Consequently urea, for so long a time the bugbear of physicians, is shown to be most dangerous when absent. When urea is deficient, blood serum or water in which the other toxic substances are dissolved should be withdrawn. This is best done by _venesection_, whose value in so-called uremia experience amply corroborates. When kidney activity ceases, intoxication is likely to be produced by potassium salts. Ptomains, amido bases, etc., are proved to be present in normal urine and are known to produce toxic effect. These ptomains increase enormously in pathological urines, and to this increase, rather than to that of potassium and coloring matters (which remain fairly constant), may be attributed the higher toxicity of pathological urine. In certain cases, however, as in that of jaundice, the toxicity of the urine is partly due to decomposition of tissue cells, whereby potassium salts and organic decomposition products are liberated and excreted in the urine. The toxicity of the urine also increases with the increase of indican, which is indirectly a product of intestinal fermentation. The _osmotic pressure_ of the blood has much to do with the general subject of auto-intoxication, since it surrounds and permeates all the organs of the body, which are necessarily in equilibrium with it. Their individual cells functionate, then, in accordance with it, and variations in such pressure must affect their activities. It is a special function of the kidneys to eliminate enough of the accumulated metabolic products in the blood to keep this osmotic pressure at its normal. Should investigation or symptoms of disease show a wide divergence from this standard, the inference is plain, _i. e._, that there is renal insufficiency from impairment. This test may be made with a small amount of blood by _cryoscopy_ (determination of freezing point). So, too, a determination of _electrical conductivity_ may, in a similar way and for a similar purpose, be made of clinical value. Unfortunately, these investigations are not exactly simple in character, and are not available outside of well-equipped hospitals. Correct performance of _hepatic function_ is also necessary that surgical cases may progress without disturbance. Bile escapes direct absorption by the blood, but not all contact with it, since in the intestine it is in contact with mesenteric capillaries, but must pass again through the liver, which takes it up again and pours it once more into the intestine.