Now, such an observation is interesting, when viewed in connexion with two circum stances, specially observed and proved by Newport, namely, that in the artificial itn pregnation of the ova of amphibia, although the process of impregnation is commenced at the instant of contact of the spermatozoa with the ova, yet a certain duration of contact is essential to its completion. And further, that although an exceedingly minute quantity of spermatozoa suffices to impregnate the ovum, yet impregnation takes place more tardily when the number is extremely limited than when the number is in full abundance ; while when the quantity is reduced below a certain amount, or the duration of contact is limited, then the phenomenon is incomplete, and partial impregnation, evidenced by imperfect segmentation of the yelk, and arrest of the further stages of development, is the in evitable result.
Since, then, it cannot be supposed that a less perfect or complete contact of the ova with the spermatozoa is needful to their im pregnation in the higher than in the lower vertebrata, there seems to be good ground for conjecturing that this peculiar peristaltic movement in the vvalls of the Fallopian tube, which has been noticed also by other ob servers, may have for one of its objects the more perfect commingling of the two gene rative elements, the spermatozoa and the ova, which, proceeding as they do in opposite di rections, and encountering each other in some portion of the canal, would thus be carried backwards and forwards, and thus a certain permanence of contact, such as Newport has shown to be necessary in the amphibia, would be insured to them. And this supposition may be further strengthened by the reflection that while an onward movement in either di rection would serve for the conveyance of each clement singly along the tube, a back ward and forward motion alternating could only retard either or both processes, and that there could be only one apparent advantage in such retardation, namely, the retention of both elements for a longer or shorter time in permanence of contact.
To sum up the offices of the Fallopian tube, the following may be said to have been with certainty ascertained to belong to that division of the generative organs : To re ceive the spermatic fluid from the uterus and convey it upwards through the entire canal, and as far sometimes as the ovary ; To receive contrariwise the unimpregnated ova, as they are discharged from the ovary, by means of its expanded open mouth, which in these cases, where the entire ovary cannot, be grasped, is guided, by a process hitherto unexplained, to select and apply itself to that particular spot from which the ripe ovum is about to be expelled ; to convey the ovum in a direction opposite to the course of the fertilising fluid, so as to ensure the meeting and commingling of the generative elements, an event to which the limited calibre joined to the peristaltic action of the oviduct probably in a great deoree contributes ; to afford pro tection to the ovum during that brief sojourn in which the first effects of fertilisation are manifested upon its constituent parts ; to aid probably in certain changes which are operated upon the surface of the ovum, con sisting first, in all cases apparently, in a strip ping off' of the adventitious covering with which the ovum is invested on entering the tube, and secondly, in some instances, in the addition of certain materials which in crease slightly the bulk of the ovum ; and lastly, in transmitting onwards the ovum, so altered and prepared for more complete de velopment, to the cavity of the uterus, or in conveying away those which, for want of impregnation, are destined to perish.
In reference to these conclusions regarding the offices of the Fallopian tube, which the present state of physiology appears to war rant, the question here naturally arises, how far they are applicable to the female of man, or to what extent her case may be viewed as exceptional on account of certain differ ences in her organisation and habitudes. - One of the most observable of these dif ferences is the absence of that marked dis tinction of periods alternating with each other, such aS are shown in a greater or less degree in the females of most mammalia in regard to the activity of the sexual functions.
That these alternating periods of desire and aversion to the coitus are strictly sig nificant of corresponding temporary states of physical capacity and incapacity for concep tion, is placed beyond doubt, by the results of examination of the internal organs and their contents at these respective periods.
In those animals in which the oastrus re turns at short intervals, the male generally remains potent at all times. The temporary incapacity is on the side of the female, and occurs in the intervals between the successive acts of ripening and discharge of the ova from the ovary, together with their passage down the tube. It has been shown that during these events only will she receive the male, and therefore, on that account also, is con ception then only possible.