EXTRACTS OF THE PARS NEURALIS 



lymph sac). On the other hand, Granaat and Hillesum (1937) 

 reported that doses of "Pitressin" which cause retention of 

 water absorbed through the skin were without appreciable 

 effect on the secretion of urine. If posterior-lobe extract pro- 

 duces anuria in frogs, it probably arrests the circulation of 

 blood in the glomeruli ( Adolph, 1936). 



The effects oj posterior-lobe extracts on the metabolism oj car- 

 bohydrates. — It is not yet known to what substance the prin- 

 cipal effects of posterior-lobe extract on carbohydrate 

 metabolism should be attributed. In the rabbit, at least, ex- 

 tracts rich in the vasopressor principle usually appear to be 

 the most powerful both in causing an elevation of the level 

 of the blood sugar and in antagonizing the hypoglycemic 

 action of insulin or the hyperglycemic action of epinephrine.'^ 

 In this last case the vasopressor hormone perhaps facilitates 

 liberation of insulin; however, there may be a simpler ex- 

 planation such as an effect on the absorption of epinephrine. 

 According to Ellsworth (1935-36), who confirmed the re- 

 sults of others in rabbits, it is the oxytocic fraction and not 

 the vasopressor fraction which is responsible both for the 

 production of hyperglycemia and for the antagonism of insulin 

 in the dog. Moreover, Ellsworth found that the effect of the 

 purified oxytocic extract in the dog was produced by much 

 smaller doses (in terms of units) than are necessary to cause 

 corresponding changes in the rabbit, which apparently is 

 sensitive only to the vasopressor principle. Further studies 

 are greatly needed to decide conclusively whether or not the 

 action on carbohydrate metabolism is caused by some sub- 

 stance not identifiable otherwise. 



Experimental work in animals indicates that hypergly- 

 cemia or insulin antagonism caused by posterior-lobe extract 

 is the result of an action on the liver from which an increased 

 quantity of glucose is liberated into the hepatic veins and 

 thence into the general circulation because of glycogenolysis 



's See the recent article of Gurd (1934). 



[269] 



