GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 215 
theory of Heape (loc. cit.) that the source of the stimulus- 
exciting development in the mammary glands is in the 
ovary. 
The Importance of the Ovary. 
There is good experimental evidence to show that in the 
higher mammals the ovary is of extreme importance to the 
commencement of the growth of the mammary glands at all 
times. Marshall and Jolly (35) point out that double 
ovariotomy before puberty begins has the effect of preventing 
its onset, with the associated growth of the breasts. Accord- 
ing to Dixon ( 11 ) the same operation after puberty produces 
a cessation of menstruation, sometimes accompanied by 
atrophy of the breasts and internal genital organs. Halban 
(20) found that if the ovaries were removed from guinea-pigs 
shortly after birth the uterus and mammary glands remained 
undeveloped, and Lane-Claypon and Starling (loc. cit.) 
have shown that, even during pregnancy in the rabbit, if 
Porro’s operation be performed and the ovaries removed 
during the first fourteen days (i.e. approximately the first 
half) the development of the mammary gland ceases and 
retrogression takes place without a secretion of milk. There- 
fore it seems we should look to the ovary for the seat of this 
hormone. Kuauer (28), as a result of his experiments, came 
to the conclusion that it is only so long as there is an active 
functional ovary present that it influences the general 
metabolism of the body. But it is obvious that this secretion 
is not produced continuously by the ovary, but only at the 
periods of heat, for it is only at these times that the mammary 
glands undergo enlargement. An extremely interesting case 
bearing on this point is reported by Gelhorn (17), who 
describes a woman with seven nipples in the neighbourhood 
of the mons veneris, and states also that these abnormally- 
situated mammary glands yielded a How of milk at each 
menstrual period. Puberty is only the commencement of 
these oestral periods, and pregnancy consequent upon one of 
them. Now oestrus has been shown by Marshall and Jolly 
