66 THE ROYAL SOCIETY OF CANADA 
Histology. 
The organ is enclosed by a thin but firm capsule covered on the 
exterior by an endothelium (PI. III, fig. 3 end). The substance of the 
body is made up of irregular columns of epithelial cells with intervening 
blood spaces whose endothelium is very clearly shown (PI. III, fig. 3 
bld. s.) In addition to the epithelial cells there are others which appear 
to be lymphoid. The epithelial cells have large oval or round nuclei. 
The lymphoid consist of smaller rounded darkly staining nuclei with 
a narrow rim of protoplasm (PI. III, fig. 3 l.c.) These two varieties of 
cells are seen throughout the whole of the organ but the lymphoid cells 
are frequently more numerous in the peripheral regions. This 
suggests that there has been a leucocytal invasion from the 
exterior. 
There can be no doubt that the ventral branchial body subserves 
some very important function in the frog, though it is too early to 
make any definite suggestion as to what that function may be. So far 
as Iam aware there have been no extirpation experiments performed 
upon the body nor have there been any investigations upon the chemistry 
and physiological action of extracts made from it. Possibly the small 
size of the body in the frog would render the last class of experiment 
difficult; but I hope to carry out some extirpation experiments at an 
early date. 
The adenoid tissue in the body has in all probability the function 
of adenoid tissue elsewhere, ï.e.,it is a site of multiplication of leucocytes. 
The epithelial cells we may suppose have some other unknown function. 
S. Mayer’ has suggested that the body may have some function also in 
relation to the red corpuscles. No sign of alterations in the red cells 
can, however, be detected such as are readily recognized in the hemo- 
lymph series of organs. 
Development. 
The development of the ventral branchial body was first carefully 
studied by Maurer. The structurearisesat the time of the metamorphosis 
when the gill clefts are degenerating. According to Maurer it arises. 
from the anterior segment of the closing clefts. Dorsal and ventral 
branchial bodies (Kiemenreste) have also been described by Maurer; 
but these disappear early. 

1 Loe. cit. 
