288 G. CARL HUBER 
short periods. While the presence of cilia may explain the 
migration of the ova in the uterine tube, Widakowich can offer 
no conclusions as concerns the regulatory mechanism by means 
of which the ova are spaced at fairly regular intervals in the 
lumen of the uterus. In none of my sections of the uteri of 
albino rats, obtained during the fifth day after insemination, 
have I been able to note the presence of cilia on the uterine 
epithelium, even when sections were studied under the oil im- 
mersion. After reading the account of Widakowich, their 
presence was looked for in all pertinent stages, but without 
suecess. Especially in rat No. 50, in which the ova were pass- 
ing from the oviduct to the uterine horn was careful search made, 
but nothing like a distinct ciliary border, composed even of 
short cilia, was ascertained. In the left genital tract of this 
rat, as has been stated, three ova were found in the terminal 
part of the uterine end of the oviduct, one in the uterine lumen 
just distal to the mouth of the oviduct. and one a little over 
a centimeter from this opening. The latter was lodged in a 
shallow depression of the uterine mucosa, as is characteristic 
for stages lying free in the lumen. The question as to whether 
this ovum was permanently lodged is difficult to answer. If 
this is assumed, it is further necessary to assume that the other 
ova would need to pass it to reach the more distal parts of the 
uterine lumen. 
The literature contains no definite statements as concerns 
the reactions of the epithelium and mucosa of the uterus to the 
ova soon after their appearance in the uterine cavity. Widako- 
wich summarizes the views by stating that “It is generally 
stated, that so long as the ova lie free, the uterus shows no 
changes.’’ He himself notes that at this time the mucosa pre- 
sents evidence of marked new formation of capillaries. Burck- 
hard, who had at his disposal a large number of stages showing 
implantation of the ovum of the mouse, discusses at length the 
appearance presented by the uterus soon after the ova enter 
the same and the lodgment of the ova therein. This observer 
notes that in the non-gravid uterus of the mouse, the lumen 
lies more or less eccentric, and towards the mesometrial border. 
