220 
CHAS. H. o’dONOGHUE. 
which takes place during pregnancy. It is interesting, there- 
fore, to inquire into the development of the corpus luteum in 
these cases. Sandes (loc. cit.) in his paper states “that it is 
probable that the process of corpus luteum formation in 
Dasyurus ovaries, whose ova are extruded, is the same 
whether the ovum is fertilised or not.” This supposition has 
proved to be correct 1 and so there is the same marked corre- 
lation between the formation and growth of the corpus luteum 
and the hypertrophy of the mammary glands in non-pregnant 
as in pregnant animals. It is to be borne in mind also that 
the stimulus causing growth is not nervous but due to the 
presence of a hormone, and that in the non-pregnant 
animals this secretion could not come from either foetus or 
placenta. 
These considerations make it extremely probable that, at 
any rate in Dasyurus, we may regard the corpus luteum as a 
ductless gland producing an internal secretion, which in 
addition to its other functions is intimately connected with, if 
not, indeed, the actual inciting cause of, the growth of the 
mammary gland. 
There is considerable evidence to show that a similar state- 
ment is true also of the rabbit, for Lane-Claypon and Starling 
(loc. cit.), in the course of their investigations noted, that the 
growth of the mammary gland is marked almost immediately 
after impregnation, and they arrived at the three following 
experimental results : 
1 In order to substantiate this observation, I have cut serial sections 
of the ovaries of several animals in which ovulation was not succeeded 
by pregnancy, including those of Nos. 28, 29, and 30 in the foregoing 
list of mammary gland material. These were compared with the original 
slides made by Dr. Sandes and now in the possession of Professor J. P. 
Hill, and from an examination and comparison of the two series it 
appears that the process of formation and growth of the corpora lutea 
is the same in both cases. Dr. Sandes was also good enough to look 
through the slides for me, and he confirmed his previous opinion that 
there is no difference between the formation of the corpora lutea in a 
pregnant and non-pregnant Dasyurus, i. e. between the corpus luteum 
verum and the corpus luteus spurium. 
