In support of this view, Mr. McGillivray cites a case in which there was presented unmistakable evidence that the organization of the placenta admits the return of the venous blood to the mother; and Dr. Harvey, with much force, suggests that the effect produced is analogous to the known fact that constitutional syphilis has been communicated to a female who never had any of the primary symptoms. Regarding the occurrence of such phenomena, Dr. Harvey under a later date says: "since then I have learned that many among the agricultural body in this district are familiar to a degree that is annoying to them with the facts then adduced in illustration of it, finding that after breeding crosses, their cows though served with bulls of their own breed yield crosses still or rather mongrels; that they were already impressed with the idea of contamination of blood as the cause of the phenomenon; that the doctrine so intuitively commended itself to their minds as soon as stated, that they fancied they were told nothing but what they knew before, so just is the observation that truth proposed is much more easily perceived than without such proposal is it discovered."[12] Dr. Carpenter, speaking of phenomena analogous to what are here alluded to, says: "Some of these cases appear referable to the strong impression left by the first male parent upon the female; but there are others which seem to render it more likely that the blood of the female has imbibed from that of the foetus, through the placental circulation, some of the attributes which the latter has derived from its male parent, and that the female may communicate these, with those proper to herself, to the subsequent offspring of a different male parentage. This idea is borne out by a great number of important facts. * * As this is a point of great practical importance it may be hoped that those who have the opportunity of bringing observation to bear upon it, will not omit to do so." In the absence of more general and accurate observations directed to this point, it is impossible to say to what extent the first male produces impression upon subsequent progeny by other males. There can be no doubt, however, but that such an impression is made. The instances where it is of so marked and obvious a character as in some of those just related may be comparatively few, yet there is abundant reason to believe, that although in a majority of cases the effect may be less noticeable, it is not less real, and demands the special attention of all breeders.