265 
Assuming then that. all the nodules which the writer has desig- 
nated as supernumerary spleens in cats and dogs are actually such 
and consequently accepting it as established that hemal nodes other 
than supernumerary spleens, are absent in these animals the question 
as to the structural relation of the latter to what I have termed hemal 
nodes in the sheep, goat and bovines nevertheless remains. But before 
considering this question it is well to compare the macro- and micro- 
_ scopic structure of the supernumerary spleens in dogs and cats with 
the main spleens of these animals. 
Attention has already been directed to the fact that the super- 
ficial resemblances of color and surface between the main and super- 
numerary spleens usually differ directly with the differences in size. 
The greater the differences in size the greater the differences in gross 
appearance and the same is true, to a certain extent at least, of their 
microscopic structure also. The most striking thing upon the exa- 
mination of a cross-section of the smaller supernumerary spleens is 
the entire absence of Malpighian corpuscules. I wish to emphasize 
this fact especially, since Tizzoni (27) stated that the accessory spleens 
which form as a result of splenectomy arise as Malpighian corpuscules 
which become surrounded by pulp later while those that form as a 
result of pathological processes in the main spleen were said to arise 
as pulp in which Malpighian corpuscles appear later. The absence 
of Malpighian corpuscles in the smallest supernumerary spleens would 
then, seem to confirm Tizzont’s conclusion regarding the structure of 
spleens formed as a result of pathological processes, provided that we 
assume that those without Malpighian corpuscles are the youngest and 
that they have formed as a result of pathological conditions. Neither 
of these conclusions can be considered as established however. 
The larger supernumerary spleens have more Malpighian corpuscles 
and the largest found which measured 6—9 mm. in diameter, posses- 
sed as many as the main spleen per unit area as judged by cross- 
sections of portions of both. However, most of the supernumerary 
spleens examined had none or only a few and mostly atypical 
Malpighian corpuscle. Sometimes too, they contained follicles without 
a central artery but in many instances not even these. However, 
since great differences were noticed in the number of Malpighian 
corpuscles present in the main spleens of dogs and cats as judged by 
cross-sections of small portions and since they are transient structures, 
it does not seem that this difference between the main and super- 
