44 G. CARL HTJBER 



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 

 success. 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 'Tt 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. 



