396 INTERNAL SECRETIONS OF PANCREAS AND SPLEEN. 



those of neighboring acini. They vary considerably in size, and 

 not infrequently one finds very large round vesicular nuclei 

 whose diameter is two or more times that of those about. 

 Occasionally the cells, forming columns between which are the 

 anastomosing capillaries, are very closely packed together, and 

 nuclei are situated almost side by side; more frequently the 

 cells of the island are less numerous and the nuclei are less 

 closely crowded together. 



"The outline of the island is usually round or oval, and 

 is not infrequently accentuated by a delicate circle of fibrous 

 tissue. In other instances the outline is less sharp, and the 

 body accommodates its shape to that of the neighboring acini. 

 Occasionally one sees, apparently within the island, cells ar- 

 ranged, as in the acini, about a central lumen, and, indeed, 

 in many instances it is difficult to convince one's self that they 

 do not form part of it. The impression is produced that the 

 columns of the island are in continuity with cells having an 

 acinar arrangement. Since the islands and the secreting acini 

 have a common origin, it is not inconceivable that they may 

 occasionally remain continuous in the adult organ. When the 

 fcetal pancreas is affected by congenital syphilis, the islands, I 

 have found, retain their continuity with the secreting struct- 

 ures. 



"In the human pancreas the groups of acini about ter- 

 minal ducts are not sharply defined by connective tissue; so 

 that individual lobules, as in the human liver, are indistinctly 

 marked off and in places apparently fuse with one another. 

 In the pancreas of the cat the lobules, like those in the liver 

 of the pig, are much more sharply outlined by interstitial tis- 

 sue. Details of structure have been studied in the pancreas 

 of the cat. 



"The parenchyma is divided by septa of fibrous tissue into 

 small polygonal areas in size and shape. When injected with 

 Berlin blue, a small ramification of the ducts is found to pene- 

 trate the isolated group of acini. These subdivisions, or lob- 

 ules, often appear completely isolated by fibrous tissue from 

 those near by, but when one of them is traced through a series 

 of sections its separation may be uniform, and in places one 

 finds the parenchyma of adjacent lobules in contact, the 



