The possibility of a spontaneous ovipont having been established by these and like in stances which might be quoted, it becomes important next to determine how far the law just enunciated is universal in its application ; we may therefore inquire, — Does the discharge of ova front the ovary al ways take place spattaneously, and independent of sexual intercourse? It is in endeavouring to determine this question, so far as the attempt has been made to base this law upon observations and experi ments on animals, that the difficulty to which I have just adverted is experienced ; for, whilst there is no lack of argutnent upon the subject, it must be confessed that the number of well-recorded instances proving a spon taneous ovipont in mammals is exceedingly small.
It will suffice for illustration to observe the manner in which this question has been han dled in the celebrated works of Bischoff*, Raciborskit, Coste$, and Pouchet.§ The first only of these authors has given in detail the observations and experiments upon which he has endeavoured to found a law of spontaneous ovulation in the Marnmalia. In several of these the coitus was permitted ; and although it is rendered highly probable, from the cir cumstances narrated, that in some this had no effect in producing the discharge of ova, yet the introduction in any form of the only con dition that could vitiate the experiments de tracts certainly from their value. In five, however, of Bischoff's experiments it was known that coitus had not occurred, and in three of these ova were found discharged, ac companied by the usual appearances the ovaries indicative of the recent rupture of the follicle.II In a fourth case, the state of the ovaries left no doubt that the ova, which could not be found, had escaped; while a fifth case was examined before the ova had escaped. To these Bischoff adds an example of the ovipont in an animal, in which it was only probable that no coitus had occurred.
The work of Raciborski contains a single example, which has also just been quoted.
The works of Coste and Pouchet contain no examples of a spontaneous ovipont in ani mals, but the observations of each of these authors are given in the form of results. Each work contains a minute description of the process of ovulation, drawn apparently from separate observations ; but these descriptions aro not accompanied by any detailed ex a.nples, nor any statement of the means used to render these observations proofs of an ovi pont, independent of coitus.
But all these authors agree in stating that ovulation occurs independently of sexual union, whilst they differ as to the degree of strictness with which the universality of this law is enforced. Pouchet demands that the law should be received without any excep tion, and observes with surprise the " unac countable vacillations " of those among his predecessors who yield to it only a partial assent.
But in the absence of any extensive series of well-recorded observations, whose numeri cal force shall be such as to compel a uni versal acceptance of the law, it is not sur prising that some who regard it as having been too hastily framed, and as too rigid in its ex clusiveness, should withhold their full assent to it. For let it be conceded that the ova, when they have attained their complete deve lopment, escape naturally from the ovary, the rupture of the follicle not necessarily requiring the intervention of the male, should it there fore be inferred that the latter is completely inoperative when exercised on opportune oc casions ? In this form the question is put by Coste, who maintains that although the coitus may not be the essential cause of the rupture of the follicle, yet it undoubtedly has the power to precipitate that event, and even to prevent its failure. He further considers that there this difference between the fecundated female and one in whom impregnation does not take place ; that in the foriner the rupture of the follicle is prompt, whilst in the latter it is tardy, or even in certain cases fails to occur.
In order to support this view, Coste cites two observations upon the rabbit. In the first of these, the animal was in heat, and mani fested great ardour for the male, but coitus was not permitted. It was kept for forty eight hours, and then killed. The genital or gans were highly congested. Six follicles in one ovary, and two in the other, were appa rently ready to burst, but no ruptnre had yet taken place. In the second experiment, the animal remained in heat for three days ; on the fourth day the heat ceased, and on the fifth it was killed. The organs were in the same condition as in the last case, but no follicles had burst. Coste attributes the ab sence of rupture in these cases to the preven tion of the coitus at a time when, if permitted, it would in his view have determined that event.