M. A. Lane 41” 
8 cells both remain unfixed, and the islet appears uniformly brownish 
yellow. The zymogen granules, on the contrary, appear to be well fixed 
and react readily to the neutral gentian. 
Aqueous-Chrome-Sublimate plus 5 per cent of 10 per cent cent Nitric 
Acid.—This fixation gives much the same result as that with aqueous- 
chrome-sublimate, but the chromatic effects are not so clear. The B 
cells are admirably picked out and almost invariably show the entire 
cytoplasm crowded with granules. In this fluid the zymogen granules 
are well preserved and take the stain fairly well. 
The affinity of the two types of cells for certain fixing agents is peculi- 
arly brought out in tissues fixed in a combination of these fluids. Thus 
in tissues fixed in chrome-sublimate solutions with equal parts of alcohol 
added, an islet here and there near the edge of the section shows both 
types of cells equally granulated; and the same is true of islets near the 
edge of sections from tissue fixed in aqueous-chrome-sublimate to which 
has been added 5 per cent of 10 per cent nitric acid. 
These various tests, together with those furnished by the use of the 
three principal fluids above mentioned, enable us to make certain positive 
statements concerning the nature of the two substances contained in the 
A and B types of cells in the guinea pig’s pancreas. That contained in the 
A cell is fixed by alcohol, by a 10 per cent solution of nitric acid, and by 
a 10 per cent solution of formol. In all these fixations it is stainable with 
Bensley’s neutral gentian. It is soluble in acetic acid, in saturated 
aqueous mereuric chloride, in non-alcoholic chrome-sublimate fiuids, in 
these last-mentioned fluids also in the presence of nitric acid, in saturated 
aqueous picric acid, and in 1 per cent solution of chromic acid. The 
substance is chemically different from that in the zymogen granules, for 
in all these solutions the zymogen granule is fixed and remains stainable 
with neutral gentian, while on the contrary the zymogen granule is 
soluble in alcohol in which the A granules are well preserved. 
The substance in the granule of the @ cell is fixed in aqueous saturated 
solution of mercuric chloride, in chrome-sublimate fluids in the presence 
of nitric acid, and in non-alcoholic chrome-sublimate fiuids. It is 
soluble in alcoholic solutions, in acetic acid, in aqueous saturated solution 
of picric acid, in 10 per cent solution of formol, and in 1 per cent solution 
of chromic acid. And it differs chemically from the zymogen granule of 
the pancreas because the latter :s uniformly fixed by the above solutions 
with the exception of formol, in which it is not completely dissolved but 
only partially preserved. 
These considerations go to show in contrast to Laguesse’s theory that 
