208 
CHAS. H. o’dONOGHUE. 
preparation. In the tissues that have not this appearance 
there is no trace of lacerated cell walls or discharged nuclei, 
but, on the other hand, the outline of the cell and of the 
nucleus is quite definite and intact, though the shape of the 
cell becomes more flattened with the mechanical distension of 
the alveoli. Prolonged searching failed to show any sign of 
either mitotic or amitotic division of the epithelial cells or 
their nuclei. The foregoing summaries show clearly that 
this multiplication of the glandular cells rests upon very 
doubtful evidence, as some observers describe it as mitotic 
and others as amitotic. 
It would appear, therefore, that milk is produced as the 
result of a purely vital activity of the epithelial cells of the 
alveoli of the mammary gland. These cells do not undergo 
necrobiosis, partially or completely, at any rate during the 
flow of milk, and they are not replaced by division either 
with or without mitosis. Lastly, the nuclei and cell-heads 
appearing in the gland lumen and the lacerated cell walls of 
the epithelium are to be regarded in the nature of artifacts 
and not of normal productions. 
Changes when Ovulation is not succeeded by Pregnancy. 
Professor J. P. Hill has pointed out ( 24 ) (c. f . also Marshall, 
p. 576 [ 34 ]) that in Dasyurus the changes in the mammary 
apparatus, even when ovulation is not succeeded by pregnancy, 
are the same as those occurring in pregnant animals, at any 
rate during the first stage of pregnancy. This is shown clearly 
in the following record, which is that of No. 29 in a slightly 
abbreviated form : 
Dasyurus viverriuus (No. 3). Killed, 15 . vii . ’01. 
18 . vi . *01. — Resting pouch, placed with male. 
20 . vi . ’01. — Cloacal margin getting tumid. 
28 . vi . ’01. — Cloacal margiu tumid, but pouch also tumid 
and slightly enlarged. Probably pregnant. 
30 . vi . ’01. — Pouch only slightly tumid, moist slightly but 
dirty. A whitish glairv secretion from the cloacal aperture 
