220 GEORGE W. CORNER 



in the adult, the two vascular systems may be running side by 

 side at some points, and therefore in the adult the lack of relation 

 will be less apparent than in the embryo (fig. 17). Still, it is in 

 many places striking, although in other instances a duct and 

 artery are often closely parallel. This explains perhaps, why 

 some observers describe the pancreatic vessels and ducts as run- 

 ning together, others as separate systems. 



Flint ('03, '04) has shown that in the cat and man this elabo- 

 rate structure of acini, ducts, and blood-vessels is supported by a 

 delicate reticulum of connective tissue, which is slightly con- 

 densed at the margin of the lobule to form the thin interlobular 

 septum ('04, fig. 8, p. 98). The islands of Langerhans are also 

 surrounded by a slightly condensed stroma. In the pig I find 

 the number of islands in one unit a variable quantity (none, 

 one, two, three, or more). In this paper I have considered the 

 exocrine portion of the pancreas, omitting detailed studies of the 

 islands. Bensley ('11) has given a full account of the structural 

 relations of the islands of Langerhans in another species (the 

 guinea-pig) . 



We have thus demonstrated a circumscribed portion of the 

 pig's pancreas, which is regular in size and form, and retains 

 its characteristics from foetal life to the adult stage, except that 

 its boundaries are indistinct in the adult. This unit is a minia- 

 ture pancreas, for it has secretory tissue, a supporting framework 

 of connective tissue; an artery, capillaries, a vein; and a duct; 

 and yet is itself divisible only into dissimilar fragments. In the 

 foetus, where the pancreatic tissue has ample space and is not 

 compressed, the unit has typically the form of a sphere whose 

 radius is as long as a blood-capillary. The whole adult pancreas 

 is made up of twenty or thirty thousand units of this kind, re- 

 peated side by side. The unit agrees closely with that described 

 by Opie in the cat. From a few observations the lobulation of 

 the guinea-pig's pancreas seems also to be the same as that of 

 the domestic pig; whereas in the adult dog and human the out- 

 line of the units is lost. 



