In whatever light these observations may be viewed, they- are important as showing that an animal may sometimes advance far in the pe riod of heat, and even pass through it without any ova escaping from the ovary ; but it would require a very much greater number of parallel observations to prove by such negative results the effects of the sexual congress in determin ing the act of the ovipont. And it is matter for regret that this point has not been more clearly determined ; for whilst no satisfactory results can be looked for from any observa tions upon this part of the subject in Alan, this is eminently a question capable of being deter mined by experiments on animals. All the earlier observers who directed their attention to the condition of the ovaries in relation to reproduction bear unconscious testimony to the fact that the time at which the ova quit the ovaries bears no strict relation to the act of coition. Barry states that, taking the coi tus as the starting-point of his reckoning, he was obliged to sacrifice a score of rabbits be fore he succeeded in meeting with one instance of the ovum at a particular time after its es cape, and he had almost given up the attempt in despair.
If means be used to prevent the contact of the seminal fluid with the ova after their dis charge from the ovary, or to prevent its arrival at the latter organ before rupture of the fol licle, this does not affect the immediate condi tion of the follicle. The number of ruptured Graafian vesicles which have been found, after experiments made by. placing ligatures upon the tubes before coitus was permitted, has usually amounted to the sum of the ova dis charged. If one side of the uterus be tied, the ova found in that cornu will not have been impregnated, but those on the free side will be developed. The number of ruptured follicles in each ovary will agree with the number of ova found in the corresponding tubes ; but no difference will be perceptible between those on the impregnated and those on the unimpregnated side of the uterus. The contact, therefore, of the seminal fluid with the ovary has nothing to do with the discharge of the ova, or with the formation of a " corpus luteum." The only question that can here have place is, whether the excitement of the coitus, or the contact of the seminal fluid with the inner surface of the vagina and uterus, has any influence in precipitating the discharge of ova from the ovary when they are ripe for impregnation. This, however, is, in the present state of our knowledge, an un settled point. By all the earlier observers clown to Barry, it was assurned that the coitus was the sole determining cause of the ovipont. By most physiologists since that time the coitus has been regarded as having nothing to do with the discharge of the ova, or only a limited power has been ceded to it, as in the view of Coste just detailed.
So far as numerical amount of recorded observation goes, it may be asserted that the spontaneity of the act of emission of ova, inde pendent of sexual intercourse, has been more fully anti satisfactorily proved in Man even than in animals. In the works and essays
upon this subject, to which reference is given in the preceding page, a large amount of evi dence will be found ; but since some proofs of this fact have been already given, and since it is proposed again to return to the subject in considenng the question of rnenstruation in its relation to ovulation, it will not be ne cessary to pursue the subject further here. (See page 666.) In tracing the process of ovulation, it will have been observed that the ovarian follicle passes through a series of changes, so gradu ally progressive and of such a definite cha racter, that the knowledge of these may be turned to great account in any investigations relating to the ovipont ; for, next to the dis covery of the ovum itself, whether in the ovary, Fallopian tube, or uterus, the condition of the capsule, from which it is about to be or has been already discharged, will afford the best evidence as to its probable locality and condition, even should the ovum not be found. Doubtless, one of the greatest impediments which has been encountered in investigations of this class arises from the extreme diffi culty, and often the impossibility, of finding the ovum in many situations on account of its minute size. Hence, in the absence of this demonstrative evidence, which cannot always be obtained, any other, which, though only inferential, may be made available for a like purpose, is of great value. Wanting the ovum, therefore, the state of the ovicapsule may be made, in part at least, to supply the evi dence which is deficient. Now it has been shown that, whatever affects the ovum, to de termine its development or the converse affects in a like degree the follicle from which it had been discharged, not on account of any appa rent sympathy between the ovum and the fol licle which once contained it, but from the whole generative track being more or less brought under the power of one common sti mulus, felt alike by all the parts that are em ployed for the nutrition and protection of the ovum. It will be desirable, therefore, now to determine what evidence the condition of the ovarian follicle affords, first, as to the previous escape of an ovum, and secondly as to the probability or certainty of that ovum having been impregnated or otherwise. But since it is desirable to fix the value of certain terms which are commonly employed to designate particular states of the follicle,it will be need ful, first, to determine, What is a corpus luteum ? This term, as Raciborski has observed, is indicative of the infancy of science. It be longs to a period when anatomists were in the habit of designating by the word body or colyius any part of the animal economy whose nature or relation with other parts they did not comprehend, adding to this some dis tinctive title drawn from the general appear ance of the part. Hence the terms corpus striatum, corpus callosum, cmpus luteum. It is an unfortunate circumstance that such a term was ever applied to the Graafian follicle, and the more so since it is often employed without any definite meaning.