190 MINUTE STKUCTURE OF THE PANCREAS. [BOOK II. 



The epithelium lining lobar and intralobular ducts is composed 

 of short columnar epithelium cells, each with an oval nucleus near 

 the membrana propria on which the cells lie. The epithelium cells 

 become shorter from the lobar towards the intermediary ducts. It 

 is to be noted that the epithelial cells of the ducts of the pancreas 

 do not exhibit the * rod-like fibres ' (Klein) which are so clearly seen 

 in the intralobular ducts of the salivary glands. 



The intermediary ducts 'are branched canals of various lengths 

 with a small but distinct lumen; each consists of a membrana pro- 

 pria, a continuation of the same membrane of the intralobular duct, 

 lined with a single layer of flattened clear cells more or less elon- 

 gated, and each with a flattened oval nucleus' (Klein). In some 

 cases, as in the pancreas of the rabbit, these tubes are very long, 

 in others extremely short, the branches of the intralobular ducts 

 appearing to pass almost immediately into the alveoli. 



structure of The alveoli which open into the intermediary 



canals are more or less tortuous tubes composed of 

 The secreting ^ ^ -i i , . , . i 



cellSi a delicate basement membrane which is covered on 



its inner side by the proper secreting cells which, as 

 Heidenhairi aptly remarks, possess specific peculiarities which make 

 it impossible to mistake them for the cells of any other gland. 

 These cells are sometimes described as columnar, but they are not 

 as regular as typical columnar epithelium cells and present much 

 more rounded outlines. The tube is so filled by these cells that a 

 definite continuous lumen is not usually visible. 



Appearances The appearances of the pancreatic cells differ greatly 

 of the cells in accor di n pr as the gland has been for many hours in- 

 fasting animals. > . TTT in 



active or long secreting. We shall at present only 



describe the appearance of the cells of the pancreas of the fasting 

 animal. 



Each cell presents, in its fresh living condition, a clear apparently 

 homogeneous outer zone, directed towards the basement membrane, 

 and a granular inner zone. The clear outer zone is relatively small, 

 only forming from one-eighth to one-sixth of the depth of the cell. 

 Carmine stains the outer, clear, zone easily, but scarcely at all the 

 granular inner zone. In many animals, the cells are granular through- 

 out, in the fasting state. 



The outer zone which in the living cell appears homogeneous 

 is not so in reality, as we learn by the action of perosmic acid, or by 

 maceration for 2 or 3 days in solution of neutral ammonium chro- 

 mate, which reveal the existence of longitudinal fibrillation. 



At the junction of the outer and inner zone of the cells of the 

 fasting pancreas is situated a spherical nucleus which is scarcely, 

 if at all, visible in the living cell, but which is stained by carmine 

 or logwood. 



