222 GEORGE W.' CORNER 



no more capacious than any other strand of the net. A few 

 ])lind twi^s project at different points; some of these are pe^'haps 

 indicative of incomplete injection, but others, no doubt, are the 

 beginnings of new meshes. 



There are a few hints of this early stage of the pancreas in the 

 literature. Hill ('06) found that the early bile-ducts are plexi- 

 form. Some of his preparations are illustrated in Mall's study 

 of the liver unit ('06). Laguesse ('95-'96) has made a careful 

 study of the early growth of the sheep's pancreas by sections and 

 graphic reconstructions. According to him, the anlagen grow 

 out as solid cords, which anastomose "like the cords of Remak 

 in the liver." "Wlien the embryo is 18 mm. long, all these cords 

 have become hollowed out, constituting the "primitive pancreatic 

 tubules." No doubt injections of this and the immediately suc- 

 ceeding stages would give pictures identical with that here fig- 

 ured in the pig of 35 mm. Next, according to Laguesse, the 

 progenitors of the true secreting tubules grow out as buds 

 from the sides of the primitive anastomosing tubules, and 

 the anastomoses disappear slowly, but by searching may be 

 found in the sheep embryo of 115 mm. These statements were 

 verified by Renaut ('99); and Volker ('02) found the earliest 

 tubules of the pig's pancreas to anastomose. The injection 

 method now enables us to give positive proof of these observa- 

 tions, and to follow the subsequent changes with ease. 



Thus, in the pig of 40 mm. (fig. 8, Dt) there is seen the first 

 sign of a main excretory duct amid the plexus. One faintly dis- 

 tinguishes a slight increase in the diameter of some of the tu- 

 bules in the head of the pancreas, as if a channel were forming. 

 The formation is complete in the 50 and 60 mm. specimens of 

 this series (figs. 9, 10). Here there is a definite excretory duct, 

 which runs through the head of the pancreas to the duodenum 

 in the course taken by the duct in the adult. This channel gives 

 off a great number of branches, which all anastomose, so that 

 the pancreas is composed of a close net of capillary ducts, with a 

 channel coursing through it to the intestine. The resemblance 

 to an artery and its capillary net is complete; and no one who 

 has seen Thoma's figures of the primitive blood-plexus can fail 



