GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 221 
(1) That if the ovaries and internal genital organs be 
removed before the fourteenth day, i.e. about the first half 
of pregnancy, the mammary glands return to a state of rest 
without giving any milk. 
(2) That if the same operation be performed after this time 
within two days milk is expressible from the nipple, that is to 
say, that by this time the mammary gland has reached a stage 
of development at which it is able to become functional. 
(3) That “the growth of the ovaries is, however, chiefly 
marked in the first third or half of pregnancy. After this 
time the Corpora lutea begin to diminish in size and with 
them the whole ovaries/’ 
Now the researches of Fraenkel and Cohn (loc. c it.) and 
those of Kleinhansand Schenk (loc. c it.), have shown that the 
important factor in the changes during early pregnancy is the 
corpus luteum and not the whole ovary. 
It would therefore appear from a consideration of these 
facts that in the rabbit the secretion of the corpus luteum is 
not only necessary for the first stages in the attachment of 
the embryo, but also is the stimulus causing the growth of the 
mammary glands, at least up to a point where the gland is 
sufficiently developed to produce milk. 
Since arriving at the foregoing conclusion, my attention has 
been drawn to a demonstration of Ancel and Bouin (1), who 
have shown that in the rabbit, when the appearauce of the 
corpus luteum followed on coition with a male, part of whose 
vasa deferentia had been double ligatured for some months, 
or on the artificial rupture of the follicle, there was a large 
growth of the mammary glands. This growth was very 
noticeable by the fourth day, and continued up to the 
fourteenth day, after which regression set in. It is to be 
noted that Lane-Claypon and Starling found that removal of 
the internal genital organs and ovary only produced a regres- 
sion of the mammary glands without milk secretion if per- 
formed before the fourteenth day. 
From the evidence adduced above in regard to the rabbit 
it would seem that the growth of the glands during the last 
