STUDIES ON THE MAMMARY GLAND 425 
and that Schil observed true milk secretion in the ducts of a 
human fetus at the beginning of the eighth month, proves fairly 
conclusively that a secretion capable of stimulating the glands 
to action is formed in the placenta or ovary of the mother and 
transmitted to the blood of both mother and offspring, thus 
bringing about the formation of milk in both maternal and fetal 
mammary glands. 
Berka (711) believes the contents of the lumina of the milk- 
ducts through the virgin stage is a part of the witches’ milk 
which has been retained in the ducts. On the other hand, Schil 
(12) thinks this results from a constant slight secretory activity 
of the epithelial cells. O’Donoghue (’12), after studying Dasyu- 
rus agrees with Schil in the following: 
A trace of a secretion somewhat resembling colostrum is always to be 
found as a coagulum in the lumen of the tubules and ducts until it is 
removed by the more active secretion of colostrum or milk. It would 
appear, then, that the gland, quite apart from the proper milk flow, is 
the seat of slow secretory activity, although this secretion is quite dif- 
ferent in microscopic appearance from true milk. 
Aristotle is said to have observed witches’ milk in the goat. 
Creighton (’78) reported it in the guinea-pig in the following 
manner: 
The fluid expressed from the nipple of the new-born guinea-pig had 
the appearance of a watery kind of milk; on microscopic examination, 
the milk-globules of ordinary milk were not found, but a more uniform 
fluid mass irregularly broken up under the cover-slip into large or small 
drops, and without any mixture of cellular elements. 
Barfurth noticed such a secretion in the guinea-pig, bitch, and 
rabbit and regarded it as a coagulum resulting from simple 
transudation. After studying it in Vespertilio murinus, rabbit, 
and the domestic cat, Brouha (’05) came to the following con- 
clusions in regard to these forms; “la sécrétion natale existe 
également, mais elle n’aboutit pas, au moins dans les trois pre- 
miéres semaines de le vie, 4 une véritable lactation.’ Schil 
(12) observed secretion in the ducts of rabbit embryos as well 
as postnatal stages. No secretion has been observed in the 
ducts of rat fetuses by me. Brouha’s work and the present 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, NO. 4. 
