The röle of the chondriosomes in the ceils of the guinea-pig’s pancreas. 255 
deraonstrate the identity of some cytoplasmic structures of the adult 
with that of the chondriosome in the embryo ; a not entirely satisfactory 
test, since no method of staining is known, which is absolutely and ex- 
clusively selective for mitochondria and chondriokonts. 
Nevertheless, by submitting any particular tissue to the action of 
several different fixatives, as well as the specific chondriosomal stains, 
it is possible to ascertain with reasonable accuracy, the identity of the 
chondriosome, either in the form of rods and threads, or granules, and 
to avoid confusion with other cell bodies such as the centrosomes, or 
nucleoli extruded from the nucleus. 
I shall refer again to this matter in dealing, further on, with the 
methods of fixation and staining which were employed in making the ob- 
servations embodied in this paper. 
Besides the four works specially referred to above, much has been 
published in the last few years on the chondriosomes occurring in other 
tissues, espeeially in the seminal cells, in the kidney, and in various secre- 
tory glands, see Champy (1909), Regaud (1909), Launoy (1905). 
From these numerous observations one fact which Stands out very 
clearly is that the history of the embryonic chondriosome is not the sarne 
for all the different tissues of the body. Thus, in the case of the myoblasts 
and epidermal cells, the chondriosome undergoes a metamorphosis the 
ultimate product of which presents an aspect differing considerably from 
that of the structure from which it arose, and in the case of the neuroblast 
this extends even to the staining reaction, for as Meves has shown, the 
chondriosome of the neuroblast in the embryo chick, no longer responds 
after the third day of incubation to the mitochondrial stain, but can be 
demonstrated only with the stains specific for neurofibrils. 
In other organs, however, the change undergone by the chondriosome 
is very slight, if indeed it undergoes any at all. For in the kidney, pancreas 
and salivary glands of the adult, the chondriosome is still composed of 
rods (chondriokonts) as it was in the cells of the embryo, or remains granulär, 
as in the liver. 
Fixation and staining. 
The fixatives employed were, Zenker’s, Flemming’s strong formula, 
Benda’s modification of Flemming’s solution and Altmann’s potassium 
bichromate-osmic acid solution. 
The two latter are specific fixatives for the demonstration of chon- 
driosomes. Zenker’s fluid however, entirely fails to fix those bodies, 
and the strong Flemming solution fixes them only occasionally, and even 
