OVARIAN FOLLICLES IN FERRETS AND FERRET-POLECAT HYBRIDS. 337 
that an alteration of the nervous system produced by sexual congress can produce 
results in some animals of a species in about thirty hours, when in other animals, of 
the same species, placed under similar conditions, the result may be delayed for 
more than ninety hours, whilst if the coition is sterile, the result aimed at is 
not attained. 
If the influence is a nervous phenomenon, which acts by producing vascular 
engorgement of the generative glands, and so provides an increase of pabulum for the 
developing follicles, it might be expected to be fairly regular in its effects, as it 
seems to be in rabbits, which usually ovulate about ten hours after coition, whether 
the coition is sterile or not. This possibility cannot at present be definitely excluded, 
and it must be noted in association with it that, in my series of thirteen ferrets, in 
which coition was attempted, and was apparently successful, but in which ovulation 
did not follow (Table V), the average size of the largest follicles is "9567 mm. 3 , 
that is, somewhat less than three times as large as the average size of the largest 
follicles in animals in full heat but in which no attempt at insemination was made, 
a fact which points to the conclusion that although the coition was sterile and was 
not followed by ovulation, it had nevertheless a definite influence on the growth 
of the follicles. 
If the influence produced by coition is a chemical influence, then it must be 
due either to the spermatozoa or to other constituents of the seminal fluid. 
In bats, coition produces no results, with which we are acquainted, until several 
months after its occurrence, and it is difficult to imagine that the fluid portion of the 
seminal fluid can lie in the uterus for so long a period without diffusing into the 
lymph or blood-vessels and then be suddenly absorbed in the early months of spring, 
whilst it is less difficult to realise that the spermatozoa might lie dormant. 
The influence of spermatozoa is more or less excluded, however, by the conditions 
met with in rabbits. Some, but very few, of those animals ovulate, on rare occasions, 
spontaneously (25a). The majority ovulate about ten hours after coition, but 
ovulation may occur when coition has been rendered sterile by a previous operation, 
either on the male or on the female, the result, judging from the data furnished by 
Marshall (25a), being much less certain in the cases of sexually mature virgins 
than in parous animals. This point may prove to be of importance, for it suggests 
that previous fertile coition facilitates sterile coition at a later period, and, if this 
is so, it may be an indication of the lasting effects of spermatozoal action. The 
evidence is not sufficient to justify a conclusion, and, so far as the data available go, 
it must be supposed, for the present, that the ovulation in the rabbit is due to 
coition, and is brought about either by some nervous influence or by the constituents 
of the spermatic fluid other than the spermatozoa. It is obvious, bearing in mind the 
size of the protometra, that such constituents may be fairly abundant. 
A survey of facts which fails to secure a definite conclusion is always unsatis- 
factory, but it must be admitted that the data at present at our disposal are not 
