PHAEMACOLOGY OF HYPOPHYSEAL EXTEACTS 761 



diuresis was an augmented systolic pressure with a decreased pulse pres- 

 sure. Nevertheless, neither they nor Schafer and Herring (1906) deny 

 the possibility that the diuresis may not be due to an increased blood sup- 

 ply to the kidney. Houghton and Merrill (1908), having observed a 

 vasoconstriction of the renal vessels as a result of the injection of pos- 

 terior lobe extracts, expressed the opinion that the diuresis was due 

 to an increased blood-pressure following the generalized vasoconstriction 

 obtaining under the experimental conditions. This opinion was apparently 

 supported by the studies of Dale (1909) and Pal (1909) who also found 

 that these extracts caused constrictions of the renal epithelium. Thaon(c) 

 (1910) concluded from his experiments that the increased blood-pressure 



\ OURS 



Fig. 7. A diagram showing the antidiuretic action of 2 c.c. of pituitrin intrave- 

 nously injected into a rabbit in which artificial polyuria had been induced by copious 

 water administration. (After Motzfeldt., J. Exper. Med.) 



is probably the main factor concerned in the diuresis but that a toxic effect 

 of the extract on the renal epithelium is also involved because he obtained 

 renal hyperemia and hematuria as a result of long continued injections. 

 Nevertheless, King and Stoland (1913-14) observed that diuresis occurred 

 only as the kidney dilated, and Knowlton and Silverman (1918) failed 

 to find any increased oxygen consumption by the kidney after injection 

 of posterior lobe extracts and hence came to the conclusion that the diuretic 

 response is satisfactorily explained on the basis of vascular changes, such 

 as an increased blood flow and pressure or a vasodilatation of the renal 

 vessels. 



Motzfeldt (6) (1917) made a very careful study of the antidiuretic ef- 

 fect of posterior lobe extracts utilizing various methods of administration 

 and found in all cases a restriction of diuresis artificially induced by the 

 ingestion of large amounts of water. From the fact that this antidiuretic 

 effect was inhibited by section of the splanchnic nerves he concluded that 



