410 COLLOIDS IN BIOLOGY AND MEDICINE 



testine will take up such solutions more rapidly than pure water. 

 Accordingly, all the conditions necessary to give the body a large 

 quantity of dilute salt solution are fulfilled. We know from Chap- 

 ter XIV that there is a strong effort on the part of the mammalian 

 organism to keep constant the swollen condition of the blood and 

 tissues, as well as the osmotic pressure. For this purpose, the 

 kidney is most important, since it is able to remove excess of water 

 and salts. We may even at present recognize thus the qualitative 

 relationship between physical properties and the diuretic action of 

 Groups IV and V. Unfortunately, we are not in a position to pursue 

 the process quantitatively, but we may assume that there would not 

 be a simple relationship. The above-mentioned physical properties 

 of Groups IV and V are to be classified not only in reference to the 

 intestinal membranes and the kidney function, but they also pay 

 a role in the irritation of nerves and the contraction of muscle (see 

 p. 289 et seq. and p. 354). According to Wo. PAULI* S the majority 

 of cations raise the blood pressure, whereas Br depresses it. This 

 explains why bromids are of no use as diuretics in spite of the fact 

 that they might be classified as such from their behavior with colloids; 

 the depression of blood pressure they cause opposes their diuretic 

 action. Hypotonic common salt solution and potassium nitrate 

 solutions remain therefore the chief diuretics among the alkali salts, 

 In fact, it is the solution of common salt which plays, in the Spa 

 "mineral water cures/' the chief part in increasing the urinary 

 excretion. 



The result is quite different when solutions are introduced directly 

 into the blood stream. A physiological salt solution is excreted 

 practically quantitatively. If we inject a hypertonic salt solution, 

 then more water will be excreted than was introduced, and (within 

 certain limits) proportionately more will be excreted the greater the 

 concentration. This is not surprising, because the salt withdraws 

 the water of swelling, especially from the blood corpuscles and the 

 muscles. The water thus set "free" is then filtered away by the 

 kidneys. Sulphates, phosphates, tartrates and citrates, etc., of 

 sodium impede diuresis when taken by mouth; however, when di- 

 rectly injected into the blood stream, they are even more strongly 

 diuretic than common salt. This depends on their strong dehydrat- 

 ing action and their low diffusibility. MARTIN H. FISCHER by in- 

 troducing such salts was able to make a kidney, which had been 

 edematous by ligating the renal artery, function again. On in- 

 jecting an appropriate salt into the renal artery or even into the 

 kidney itself the swelling subsided and the anuria ceased. 



According to E. FREY,* if we inject the salts mentioned along 



