THE OESTROUS CYCLE IN THE MOUSE 335 
cases of tubal menstruation reported in the literature as for the 
most part occurring after hysterectomy from the stump of the 
oviduct. These are obviously not normal. Czyzewicz (’08) 
(quoted by Novak) reported after the study of six normal ovi- 
ducts at different stages of the menstrual cycle that they did not 
share menstrual phenomena with the uterus. 
The oviducts, uterus, and vagina have a common origin from 
the mullerian ducts, so possibly factors causing cyclic changes 
in the uterus and vagina may be expressed in some way in the 
oviducts. They are not, however, subjected to the periodic 
leucocytosis of the rest of the genital tract. The extrusion of 
nuclei in the ciliated portion, beginning in the early metoestrum 
and continuing in a marked degree sometimes to the middle of 
the following prooestrum, may be interpreted as of degenerative 
significance, paralleling as it does the stages of ‘‘degeneration 
and removal by leucocytosis’”’ in the uterus and vagina. 
2. The importance of certain structural features of the ovi- 
ducts of the mouse. The careful work of Sobotta (95), Huber 
(15), and H. P. Smith (17)-had made the differentiation between 
the segments of the oviduct easy. The time of passage of the 
ova through the different segments as worked out by Smith, 
ovulation being calculated in the light of the observations of 
Long and Mark (711), has been used in placing the time of ovu- 
lation and consequently the estimation of the age of corpora 
lutea. 
3. The passage of the ova down the uterine tubes. The 
mechanism of the passage of the ova down the greater extent 
of the oviducts is still not understood in the mouse. Ciliary 
action accounts only for their entry into and passage through 
the segment proximal to the ovary. Peristaltic action may 
possibly furnish motive power for the rest of their passage. Waves 
of peristalsis were not, however, apparent in my material, but 
the oviducts were always somewhat distended. Valve-like 
folds of the mucosa at the entrance of the tubes into the cornua 
have already been mentioned as a possible check to backflow of 
fluid from the uterus. The arrangement of the muscle layers 
of the oviduct as they merge into those of the uterine cornu is 
