85 _ 



contrast between islands and acinous tissue; both island and acinous 

 tissue will appear red; the red in acinous tissue running toward pink, 

 that of the islands toward orange. A higher power, smaller pieces 

 and a more careful search are of course necessary with such prepara- 

 tions, and the results are scarcely rehable. 



After as many islands are counted as time or the staining will 

 permit all the teased parts from the different regions of the pancreas 

 are collected either into one group (when only the total number of islets 

 in the pancreas is desired) or into 3 groups representing the 3 respective 

 divisions of the pancreas. These masses of tissue are then carefully 

 blotted between several thicknesses of filter paper, as is also the 

 remainder and main mass of the pancreas, after it has been carefully 

 stripped of fat and connective tissue. The pieces are next weighed 

 in weighing tubes. From the weights of the parts and of the whole the 

 total number and relative distribution is calculated. An endeavor, 

 of course, should be made to remove the same relative amount of 

 water from the remainder of the pancreas as from those portions 

 which were teased, since, as Bensley has pointed out, this is prob- 

 ably the greatest source of error in estimating the number of islands 

 of Langerhans by this method. With the human pancreas I think 

 the possible source of error is even greater at this point than with 

 that of the guinea pig, since the human pancreas is a compact organ, 

 and is much more friable and difficult to tease than is the pancreas 

 of the guinea pig. It is thus possible that in teasing the human pan- 

 creas more or less of the cell sap is lost and taken up by the blotting 

 paper. In this event the estimate would be too high. 



Fig. 1 is a drawing from a teased preparation of a fresh human 

 pancreas stained with janus green intra vitam. 



For more complete information concerning methods of staining 

 the various elements of the pancreas differentially, as well as for a 

 discussion of the relation of islet to acinous tissue, and the variation 

 in the number of islets under experimental conditions, the reader 

 is referred to the recent article by Bensley. 



Enumerations. 



Each of the male subjects in the following series had been kept 



several months upon a liberal well balanced diet which varied but 



httle from day to day. Each was required to take regular exercise 



and to keep himself clean. Not one of them had been sick during 



