416 Cytology of the Areas of Langerhans 
by the chrome-sublimate fluid, and the substance that is precipitated by 
the chrome-sublimate fluid is dissolved by alcohol. 
3. Neither of these granular substances is of the same chemical char- 
acter as the zymogen granules of the pancreas cell, and 
4. Neither of them is of the same chemical character as the prozy- 
mogen of the pancreas cell. 
To avoid cumbersome periphrase and repetition [I will hereafter desig- 
nate the cells in which the granules are fixed with alcohol as A cells, and 
these in which the granules are fixed with the chrome-sublimate fluid as 
B cells. 
That the chemical nature of the granules in the A cells differs from 
that of the granular content of the 6 cells is borne out by the difference 
of the reaction of these substances to various fixing reagents non-alcoholic 
in character, and for the most part very simple in composition. The 
results follow: 
Saturated Aqueous Sublimate——With this fixation the islet cells act in 
virtually the same manner as with aqueous-chrome-sublimate, with the 
exception that the tissues are rather shrunken than the reverse. The A 
cells remain devoid of basic granules, the 8 cells are very well preserved, 
and, throughout the whole of their cytoplasm, they are crowded with the 
violet granules, which are, however, not as brilliantly stained as in 
preparations fixed with aqueous-chrome-sublimate. The zymogen granules 
in the acini, on the contrary, are well fixed and react with a brilliant stain 
to the neutral gentian. 
Saturated Picric Acid.—This fixation is poor, in a general way, and 
both types of islet cells are entirely devoid of granules, taking up only- 
the plasma stain. The zymogen granules, here also, are sharply defined 
and stain well. 
Nitric Acid, 10 per cent.—The general fixation is poor, but the acid 
seeks the A cells much in the same way as does alcohol, and the granules 
in them are well preserved. The # cells, with this fixation, remain clear 
of granules altogether. So far as the A cells are concerned, the picture 
here presented is substantially the same as that obtained with the use 
of alcohol-chrome-sublimate and 70 per cent alcohol. 
Formol, 10 per cent.—This fiuid fixes the granules in the A cells, leaving 
the 8 cells clear. Although the stain is by no means as brilliant as that 
obtained with the three principal fiuids, yet the individuality of the 
granules in the A cells is capitally preserved. The zymogen granules in 
the pancreas cells are broken down and diffused. 
Chromic Acid, 1 per cent.—In this fixation the granules in the A and 
