Wee Ae bane Sais 
whether or not the chromatophile granules of the islet cells were zymo- 
genic; whether or not the use of a reagent which would be a solvent for 
zymogen would nevertheless act as a precipitant for the granular substance 
in the islet cells. This experiment was made with alcohol of 70 per cent 
strength. Small pieces of pancreas of the guinea pig were fixed, therefore, 
in 70 per cent alcohol and stained with neutral gentian. In sections 
treated in this way the acinous cells were quite devoid of zymogen gran- 
ules except at the extreme edge of the piece, where a partial fixation of the 
granules was obtained, whereas the islets presented the same appearance 
as in the sections fixed in the alcohol-chrome-sublimate. The same groups 
of violet-granulated cells were present. But, as the aicohol had not dis- 
solved out the prozymogen of the acinous cell, the query still remained 
whether or not the substance in the islet cell granule partook of the 
nature of prozymogen. To check this query I applied MacCallum’ iron 
reaction on these sections and failed to bring out the slightest trace of 
Prussian blue in the suspected cells of the islets, except in the nuclear 
chromatin. 
Preparations Fixed in Aqueous-Chrome-Sublimate-—The use of this 
fluid I found advisable after exhausting the list of desirable acetic fixations 
and reducing the quantity of acetic acid to an almost negligible pro- 
portion. Sections from tissues fixed with an acetic mixture were invar- 
iably blank as to granules in the cells of the islets. But with tissues fixed 
in aqueous-chrome-sublimate a most unlooked-for result appeared. The 
large cells of the islets which had been filled with violet granules in 
sections fixed with the other fluids were quite free from stained granules 
in the sections fixed with aqueous-chrome-sublimate, whereas, on the 
contrary, the cells which gave no violet reaction with the other fluids, 
in this one were filled with granules of a brilliant violet, while now it was 
the small groups of large cells that were colored with the yellow-brown 
of the orange G (Fig. 2). 
From a consideration of these facts several dapat arise. ‘These 
conclusions have to do with the microchemistry of the cells of the Islets 
of Langerhans in the guinea pig’s pancreas, and they may be stated 
somewhat as follows: 
1. The Islets of Langerhans in the pancreas of the guinea pig consist 
of two types of cells: (a) a type containing a granular substance that is 
precipitated by alcohol of a strength of from 50 to 70 per cent; and, (b) 
a type, the granular content of which is precipitated by an aqueous- 
chrome-sublimate fluid of the general character described. 
2. The granular substance that is precipitated by alcohol is dissolved 
