296 Fische/s Theory of Edema [Dec. 



We are not surprised to find that the secretion of urine ceases 

 (practically) during absolute starvation. If the colloids of the body 

 as a whole are saturated with water, none is left over to be secreted. 

 Only in so far as the tissues undergo gradual consumption during the 

 process of starvation or their colloids suffer changes which decrease 

 their affinity for water is any liberated to become available for secre- 

 tion (Page 185.) 



According to our theoretical considerations on the colloids it would 

 be expected that were a (with-water-saturated hydrophilic) colloidal 

 Solution introduced into the vascular system, no increased urinary 

 secretion ought to result. As a matter of fact, it does not, as is proved 

 by the old experiments of Ponfick^^ and the more recent ones of 

 Magnus/^ both of whom found that the injection of blood serum or 

 blood into dogs and rabbits is not foUowed by a diuresis. (Page 186.) 



The simple fact that an amount of urine is always excreted under 

 physiological conditions equivalent to the amount of water consumed 

 teils US nothing, however, of the mechanism by which this is accom- 

 plished. To limit ourselves again to the most physiological of the 

 above conditions, let us try to discover how on the colloidal basis of 

 water absorption, water is always absorbed from the gastro-intestinal 

 tract, and always excreted by the kidneys, We can take a step toward 

 the answer to this question by pointing out that the anatomical and 

 physiological conditions existing normally in the body tend to keep the 

 colloids of the gastro-intestinal tract and the blood and lymph streams 

 passing through it, in an unsaturated condition so far as water is con- 

 cerned, while the reverse conditions hold for the kidney. The mouth 

 and esophagus play practically no role in the absorption of water. The 

 stomach, according to von Mering's experiments, also takes but little if 

 any part in the absorption of water. The small and large intestine are 

 the absorptive organs for this substance par excellence. The stomach 

 is richly supplied with arterial blood. The small and large intestine are 

 also generously supplied, but not as generously as the stomach. The 

 separate branches of the mesenteric arteries which go to supply the 

 villi occupy a fairly central position in this structure and break up into 

 a capillary network which lies close under the intestinal epithelium. As 

 clearly evidenced by the dark color of the portal blood, and direct gas 

 analysis, the blood returning from the intestine is intensely venous 



" Ponfick : Virchow's Archiv, 1875, Ixii, p. 277. 



" Magnus : Archiv für experimentelle Pathologie und Pharmacologie, 1901, 

 xlv, p. 210. 



