234 GEORGE W. CORNER 



of the same laws aunounced hy Thoina to j^overn the growth of 

 arteries apply also to the growth of the gland-ehannels. For in- 

 stance, Mall has given experimental proof of a proposition deduci- 

 l)le from Thoma's laws; namely, that all the blood-capillaries of 

 an organ are equally favored by the circulation (Mall '06, p. 

 249). I have applied the same experiment to the duct system. 

 Having cannulated the pancreatic duct of an adult hog through 

 the duodenal papilla, and having injected a ciuantity of warm 

 salt solution to flush the ducts, I forced into them a blue solu- 

 tion in small spurts, a little at a time, with low pressure. At 

 first the injection mass did not appear on the surface, but on 

 the fourth spurt the entire organ, with the exception of a few 

 centimeters at the tail, very suddenly became blue, and on the 

 fifth spurt the remainder became blue. Practically all the ter- 

 minal ducts had filled simultaneously. The conditions of this 

 test are not altogether favorable, since we are reversing the nor- 

 mal direction of flow, but it is clear that all the units are about 

 equally favored with respect to pressure transmitted from the 

 chief duct. The cause of this condition may well be similar to 

 that which brings about the same state in the blood-vascular 

 system; that is to say, the capacity of a duct depends upon the 

 rate of flow of the fluid which normally traverses it. The gland 

 is a sort of hydraulic plant, receiving fluid upon one side from 

 the vessels, delivering it, on the other hand, into the ducts; and 

 as the intake is equal for all the units, so is the output eciual. 



I have not investigated the nerves and lymphatics of the grow- 

 ing pancreas, as to whether they conform to the unit structure 

 laid off by the blood-vascular system, or not. Studies of these 

 structures offer possibilities of interesting results. 



