THE PITUITARY 356 



increases the immediate secretion of milk, but causes after- 

 wards a decrease below normal. 



(b) The Kidney. The diuretic action of pituitary extracts 

 was discovered by Magnus and Schafer. The increase of 

 secretion is accompanied by dilatation of the renal arteries, 

 so that the organ swells. The action is, therefore, different 

 upon the renal vessels from that on the arteries in general, 

 which are strongly contracted by it. The rise in blood-pressure 

 produced by this general contraction is not the sole cause of 

 the increased secretion of urine, for a second dose administered 

 a short time after the first will again accelerate secretion, 

 although the second dose may not cause any rise of general 

 blood-pressure, but rather a fall. There is, therefore, a specific 

 diuretic effect upon the renal epithelium, just as there is upon 

 the epithelium of the mammary gland. The tolerance pro- 

 duced by a first injection is then less marked than in the case 

 of the blood-pressure response, but with large doses it is well 

 marked. 



It is reported that, under certain circumstances, there 

 is a secondary diminution of the flow of urine, following 

 upon vasoconstriction of the kidney. 



Hoskins and Means believe that the pituitrin diuresis is 

 due primarily to direct stimulation of the renal cells usu- 

 ally aided, perhaps, by a concomitant vasodilatation in the 

 kidneys. 



(c) The Stomach. It was shown by Edkins that extracts 

 made from the pyloric mucous membrane in boiling water or 

 0'4 per cent, hydrochloric acid contain an active substance 

 which, on injection into the bloodvessels of an animal, leads 

 to a secretion of gastric juice. 



Frouin found a similar action on the injection of gastric 

 juice. Eirenhardt confirmed the results of Edkins, but Ems- 

 mann obtained some definite effects upon the flow of gastric 

 juice as a result of injection of extracts of other organs, such 

 as the intestine. 



Houssay has recently reported a very decided action of 

 pituitary extracts upon the flow of gastric juice, and has pub- 

 lished some very convincing tracings. This appears to be a 

 direct action on the secreting cells, as in the case of the mam- 

 mary gland and the kidney. At any rate, the effect can be 

 observed upon the isolated stomach. 



