228 
CHAS. H. O’DONOGHUE. 
relation between foetus and ovary brought about the hyper- 
trophy of the mammary glands. The majority of these 
experiments were made on multiparous animals in which 
milk secretion had ceased, and in these cases placental 
extracts or implantation of placental tissue produced a flow 
of milk. Now multiparous animals for some considerable 
time after the cessation of milk secretion are useless for 
these growth experiments as the gland is already fully grown, 
and Biedl and Koenigstein report that abscesses in the breasts 
of such animals lead to milk being secreted. Basch does not 
clearly distinguish between milk secretion and hypertrophy 
of the gland, and milk secretion is no index of gland growth 
(vide Frank and Unger). All these experiments show is 
that the gland when it is fully formed may be stimulated to 
secretory activity by placental extract. This fact is of interest 
in itself and may have some bearing on the cause of milk 
secretion, but it has nothing to do with the formative growth 
of the gland, which, of course, had occurred before the 
experiments commenced. The author further describes one 
experiment on a virgin bitch in which two ovaries from a 
pregnant bitch were implanted subcutaneously into the back'. 
In a fortnight there was an increase in the breasts, and in 
eight weeks (i.e. about the normal duration of pregnancy) 
they were equal in size to those of a late pregnant animal, 
although the implanted ovaries were degenerate. Placental 
extract was injected and was followed by the secretion of 
milk, and the bitch was able to suckle pups. In this case, 
again, no allowance was made for growth in non-pregnant 
animals, and further, Heape (21) has recorded cases of virgin 
bitches giving milk and suckling pups simply after copulation 
not followed by pregnancy. So that no definite inference can 
be drawn from this experiment. 
Finally, it is only just to point out that L. Loeb (56 and 
57), who has added a good deal of further valuable evidence 
in support of the theory that the corpus luteum plays an 
important part in the uterine changes of early pregnancy, 
found that he could not induce these changes by daily sub- 
