80 THE ROYAL SOCIETY OF CANADA 
stantly in the embryo and in the new-born human subject. Biedl and 
Wiesel? have demonstrated that extracts prepared from them have 
precisely the same powerful effect upon the blood pressure as have 
extracts of the medulla of the adrenal. 
In the dog and many other animals there exists a very striking 
strip of chromaphil tissue (the “paraganglion aorticum abdominale” 
of Kohn). This is unpaired (in contradistinction to Zuckerkandl’s 
bodies in the human subject which are paired) and in a previous com- 
munication,* I have given a full description of this body under the 
name “abdominal chromaphil body,” and have shown that extracts 
from it contain adrenin or a substance having a similar chemical and 
pharmacodynamical properties. 
For the study of the naked-eye anatomy of the mammalian 
chromaphil tissues the following method (of Kohn and Stilling) has been 
adopted:—The liver and alimentary tract are removed from the 
abdomen and a piece of absorbent cotton soaked in a solution of 
potassium bichro:nate (3-5 per cent.) is placed over the retroperitoneal 
tissues and left in situ for 6 to 12 hours. At the end of this (or in some 
cases a longer or a shorter time) the adrenals, aorta, vena cava, and 
subjacent and superjacent tissues are cut out as far back as the bifur- 
cation of the aorta and washed in running water for several hours. 
The chromaphil bodies are then plainly seen, and still more plainly if 
the whole preparation be placed in glycerine. They appear as dark 
brown streaks, patches or dots of varying size and shape. (See fig. 1). 
The abdominal chromaphil body in the dog may after considerable 
practice be detected without the aid of the bichromate stain. In experi- 
ments where it is desirable to extirpate this body it may therefore be 
removed in suitable cases by ordinary surgical methods. Sometimes 
however this proceeding is a matter of very considerable difficulty. 
I have observed that if a swab of absorbent cotton soaked in a 
3-5 per cent. solution of bichromate of potassium be applied 
for from a few minutes to half an hour to the abdominal 
chromaphil body of a living dog this structure becomes stained of a 
reddish brown tint. This renders the limits of the body clearly 
visible and it may then be removed by the knifé in the ordinary way. 
Or, and this is a point to which I wish to call special attention, if the 
body has become deeply stained the possibility of any continued 
secretory activity may almost certainly be excluded from consideration, 
so that staining with potassium bichromate may be considered equivalent 
to extirpation. The safety of this assumption depends upon the extent 

3 Arch. f. d. ges. Physiol., 1902, Bd. 91. 
* Proc. Roy. Soc. B, Vol. 82, 1910. 
