1912.] Islets of Langerhans to the Pancreatic Acini. 77 



4. Exhaustion of the Guinea-Pig's Pancreas by Purified Secretin. — In order to do away 

 with the fatal depressing effect of secretin on the guinea-pig, purified secretin prepared 

 by the method of Dale and Laidlaw* or Stepp was used. The animal was amesthetised 

 by morphine and ether. The method of introducing the secretin was the same as in the 

 dog, but no cannula was tied into the pancreatic duct. The degree of exhaustion was 

 estimated by the examination of a piece of pancreas under the microscope. 



The Normal Besting Pancreas of the Dog. 



A detailed description of the pancreas is superfluous, but in connection with 

 the accompanying illustration (fig. 1, Plate 2) a brief description of the different 

 kind of cells is necessary as a base with which the experimental conditions 

 produced may be compared. The anilin-acid-fuchsin-methyl-green stain 

 after osmic-chrome-acetic fixation has proved, in my hands, so much more 

 successful than any other for the clog's pancreas that it is upon this that most 

 of my conclusions are based. 



By this technique the normal charged acinous cell shows the characteristic 

 zymogen granules stained bright red, the mitochondrial filaments the same 

 colour, while the protoplasm of the cell takes a smooth greenish tint. In 

 association with many acini, the centroacinous cells can be distinguished by 

 their clear uncoloured protoplasm and their oddly shaped red stained granular 

 elements. Some of these cells are indicated in the illustrations, and it is 

 easily seen that they are, apart from the shape of their granules, strikingly 

 like the clear granular cells of the islet. The third cell which it is important 

 to recognise is that of the ducts, and especially the finer ducts, or duct-like 

 rows of cells, which are so often found associated with the islets. These cells 

 are usually oval in shape and often considerably compressed. Their nucleus 

 is central and their clear protoplasm dotted with a variable quantity of 

 mitochondrial elements. They have, like centroacinous cells, a distinct 

 resemblance to islet cells and, as Bensley has pointed out, the latter are often 

 found among them. 



The islet cells may be easily divided into the two varieties which have been 

 noted by many investigators, and to which Lane has given the name A and 

 B cells accordingly as their granules are fixed respectively by alcoholic or 

 watery solutions. "With the acid-fuchsin-methyl-green stain the B cells, 

 which form the vast majority, take a slate blue colour. They are usually 

 smaller than the A cells, which show red granules and a clear uncoloured 

 protoplasm. Both cells possess mitochondrial elements. In the B cells which 

 have not taken up sufficient of the methyl green to give them their character- 

 istic blue colour, the mitochondrial filaments give the impression of red 

 granules, but in the heavily stained cells they hardly show. 



* I am much indebted to Dr. Dale for a supply of secretin prepared in this way. 



