KIDNEY 



649 



within a few days or weeks largely because they refuse to eat. Polyuria 

 (increase of urine beyond the normal) does not necessarily occur. It 

 is well known that when only one kidney is extirpated the other hyper- 

 trophies, and no ill-effects ensue. 



The statement that extracts of the kidney when injected into the 

 veins of an animal cause a rise of arterial blood-pressure, essentially 



Fig. 208. Effect of Bone-Marrow on Blood-Pressure. Intravenous Injection of 

 Saline Extract. Vagi Intact. The uppermost line is a signal trace showing the 

 time and length of injection. Below this is the record of the respiratory move- 

 ments, and lowest the blood -pressure tracing. To be read from left to right. 



through direct action on the peripheral vaso-motor mechanism, is of 

 considerable interest, for it may possibly have some bearing on the rise 

 of pressure and consequent hypertrophy of the heart associated with 

 certain renal diseases. But there is not as yet sufficient evidence that 

 the hypothetical pressor substance, to which the name ' renin ' has 

 been given, in any sense represents an internal secretion of the kidney. 



The pressor substance (so-called M ' 



' urohypertensine ') which can be 

 extracted by ether from normal 

 human urine (Abelous) is probably 

 only excreted by the kidney, and 

 perhaps arises from the putrefac- 

 tion of proteins in the intestine. 

 For it has been shown that in the 

 putrefaction of (horse-) meat bases 

 are formed which, when injected 

 intravenously, cause a rise of 

 blood-pressure. The most active 

 of these is a body known as 



Fig. 209. Injection of Extract of Bone- 

 Marrow with the Vagi Cut. To be read 

 from left to right. 



^>-hydroxyphenylethylamine, 

 formed from tyrosin (Barger and 

 Walpole). Whether the pressor 

 (vaso-constrictor) substance which appears to be liberated from the 

 platelets when blood is shed, and may therefore be presumed to be more 

 slowly liberated from such platelets as normally break down in the 

 circulating blood, has any relation to the pressor substance of urine 

 is unknown. It is also quite uncertain whether, as has been stated by 

 some observers, extracts of the kidney or blood from the renal vein 

 stave off for a time the onset of the uraemic symptoms that follow 



