336 EDGAR ALLEN 
identical with that in the ‘bile duct sphincter’ recently emphasized 
by Mann (20). It is possible that they serve such a function 
here. Surely, a back flow of fluid from a distended uterus would 
be fatal to the passage of ova down the tubes, if that be by per- 
istalsis. 
d. The ovaries. Many interesting ovarian problems have 
arisen in the course of this work. 
a. The follicles and ovulation. 1. Spontaneous ovulation. 
Certain species of animals (the rabbit and ferret are examples) 
usually do not ovulate spontaneously at oestrus. There has 
been much discussion concerning this question in the mouse. 
Tafani (89), Sobotta (95), and several later investigators claim 
an ovulation without added sexual stimulation. Garlach (06) 
and Bouin and Ancel (’09) state that in the mouse ovulation is 
dependent upon coition. That it usually occurs spontaneously 
the first day after parturition has been emphasized by many 
investigators, and made use of by Long and Mark (’11) in arti- 
ficial insemination. 
Possibly the size of the ovarian vessels immediately following 
parturition may be the deciding factor at this ovulation in some 
mice, but it is certain that in many mice not lately pregnant 
ovulation is not spontaneous at every oestrus and in some virgin 
mice it need not have occurred at all, although several oestrous 
cycles have been recorded, which indicates the presence of ripe 
follicles. It is obvious, therefore, that the classification of the 
mouse as a species ovulating spontaneously is not accurate. 
While it is not possible to diagnose the absence of spontaneous 
ovulation by actual cell content of the smear, unusually long 
oestrous periods in certain animals may indicate a failure or at 
least a difficulty in ovulation, for the presence of ripe follicles 
seems universal in all animals in the oestrous condition. 
2. Is ovulation in litter-bearing animals synchronous? Long 
and Mark (’11), in considering the maturation of the ovum of the 
mouse, state that ovulation is a synchronous process, although 
imperfectly so. Sobotta and Burchard report similarly for the 
rat. Huber finds fertilized ova usually bunched in their passage 
down the oviduct in the rat, which would indicate a synchronous 
prey 
