THE PITUITARY BODY 



769 



the mammary glands and the kidneys. The effect on the kidney is evi- 

 denced by the remarkable increase in the urinary flow following injection 

 of the pituitrin. This diuresis might of course be due merely to the 

 vasodilatation that we have seen such extracts produce a vasodilatation 

 which is all the more marked because the vessels elsewhere in the body 

 undergo constriction. But pituitrin continues to cause increased urinary 

 outflow in the absence of any demonstrable vascular change ; it also acts 

 after the administration of atropine, so that it is considered by most 

 observers to act on the excretory epithelium of the convoluted tubules 



Fig. 198. Tracing showing the constricting action of pituitrin on the bronchioles and its effect 

 on blood pressure in a spinal dog. (From Jacksom) 



in much the same way as certain diuretics, like diuretin. This renal 

 hormonic action of pituitrin would appear to be analogous with that of 

 secretin on the epithelium of the pancreas. Another reason for believ- 

 ing that the secretory hormone is independent of that producing vaso- 

 dilatation of the renal vessels is the fact that a repeated dose of pituitrin, 

 although, as we have seen, it usually has a depressor action on the blood 

 vessels, still produces a stimulating effect on the excretion of urine. 

 The value of pituitrin as a diuretic in clinical practice is now well 

 recognized. 



The effect on milk secretion is best demonstrated by placing a cannula 



