" To pass from this pouch into a bundle of spermatozoa, the spermatic cysts need only to undergo retraction of their lateral walls towards their base, or, towards the part in contact with the membrane of the semini ferous tube. At the close of September, the layers formed by the regu lar coaptation of the heads of the spermatozoa, no longer resemble the walls of a pouch, but look like bell-mouthed cups, crescentic on section. By the end of September, this crescent shape has widened, and all the heads are arranged along nearly the same strait line.
"At this period, a section shows the cavity of a seminiferous tubule to be as in Fig. 70. It is seen that the bundles of spermatozoa only have to become thinned and lengthened in order to possess—in October—an iden tical aspect with that shown in Fig. 69, which was the starting point of our study.
" When the spermatic cysts open at the part looking towards the centre of the seminiferous canaliculi, and when the peripheral layers containing the developing heads begin to retract on the walls of the canaliculi, then the granular nuclei follow this movement, being carried, along by their adhesion to the surface of cysts. Thus the nuclei all accumulate towards the base of the bundle that is just forming. Then occurs a remarkable event, and one which completes the cycle we have just reviewed, or, rather, begins another cycle. Those nuclei nearest the wall acquire a cellular body, finally having all the elements of the " male ovule." These give birth to spermatic cysts during the following period, while the granular nuclei, not so transformed, will soon multiply, and pro duce nuclei which will incompletely surround the new spermatic cysts.
" The young male ovules are at the base of the bundles of spermatozoa which are forming near the band of granular protoplasm, binding these bundles to the walls of the canaliculi. In preparations by dissociation, (i.e., bundles torn from the walls of the canaliculi,) we notice that a male ovule adheres to the base of a bundle (Fig. 71 and 72). When this ovule is at the side of the bundle (seen in profile at the base, as in Fig. 71) it is easy to see that it is independent of the bundle, and we can distinguish both thq nuclus and the cellular body of the male ovule; but when it pro jects from the protoplasmic cord forming the base of the bundle (Fig. 72), we can only see the large nucleus of the male ovule, and we are tempted to view it as a nucleus belonging to the base of the bundle, or rather as the analogue of what we have called the principal nucleus for the clusters of spermatoblasts, and bundles of spermatozoa of IE(lix and La Paludine. This is an interpretation to which we were strongly urged during our early studies of invertebrata, and when we had not investigated all the phases of evolution in the frog, but which a more attentive examination forced us to abandon." The spermatozoa are the active agents in fecundation, for, if they are absent from the semen, as after certain diseases of the testicles and epi didymis, sterility is the result.
Progression of the Semen in the Genital Tract.
In order that fecundation may occur, the spermatozoa must be in con tact with the ovule. Spallanzani, Prevost and Dumas, have proven this, and also, that only a minute quantity of semen is necessary. Since the semen
is in the vagina and the ovule is in the tube, the two must go in search of each other in order to fuse. Thus fecundation is not instantaneous;—a certain time is demanded for the meeting. In woman, when the follicle ruptures at or near the time of coition, the two elements meet about ten hours later. Ch. Robin states that spermatozoa travel about .78 of an inch in ten minutes. Ejaculation is against the cervix, in woman, but the os is closed, and the canal of the cervix will not allow the injection of the semen into the uterine cavity. Much of the semen flows out, after coition, through retraction of the vaginal walls. Yet enough remains in the vaginal folds and on the cervix to fecundate.
Beigel, and some German authors, describe, in the posterior cul-de-sac of the vagina, the genital or spermatic fossa. The semen is lodged here. and the uterus, after its erection at the moment of coition, being carried forward in a kind of ante-version, the cervix is plunged back into this "sper matic pool," and fecundation is thus favored. In all cases, the sperma tozoa, to reach the ovule, pass through the os cervicis. The semen is not carried en manse, but the spermatozoa progress, being resisting elements, while the other ingredients of the semen are destroyed or carried out by the mucus. According to Gerbe and Coate, the spermatozoa begin to enter the os only after 23 or 30 minutes. What is the true cause of this ? Is it capillarity, as Coste and Liegeois state ? Is the semen sucked up into the uterus, as Riolan, Morgagni, Blerhave and Pouchet state ? Is it the peculiar movement of the uterus and Fallopian tubes ( Bischoff ), or the action of the cilia (Muller) ? These opinions are rejected by Henle, Pajot, Joulin and Mathias Duval, who state that the spermatozoa are endowed 'ith motion, and, by an instinct of their own, make their way towards the ovary. Ch. Robin states that they progress individually, as the tubular form of the organ permits, and go on as long as they live and find a pro ps fluid, thus mechanically passing, not only towards the ovule, but be yond, to the pavilion, the ovary or the peritoneum, whether or not they have met an ovule. This does n pre-suppose a polarity or an instinct in the spermatozoa. " They adrince if the parts are moistened with a thin layer of fluid" (Robin). At the pavilion, and ovary, they slip over the peritoneum and are absorbed. The ovule also advances towards the spermatozoa. Where do they meet? Where does fecundation occur ? Place where Fecundation occurs.—The only exact statements are those of Gerbe and Coste. The point of meeting of ovule and sperm atozoa is on the ovary, or in the external third of the tube. Extra uterine, ovarian and abdominal pregnancies, prove this statement. Once below the external third of the tube, the ovule is covered with a layer of albumin, which the spermatozoa can not pierce. Hence penetration must have occurred before this. On the other hand, fecundation does not occur until the germinal vesicle disappears; this disappearance begins when the ovule leaves the ovary and enters the pavilion. It ends in three or four hours.