It has, however, been assumed that this observer speaks only of such women who have at least once been impregnated by a European, and it is in this form that the question has been examined by physiologists. The question has been asked, how the gestation of a Mulatto’s fœtus could modify the constitution of the mother to render her barren with the men of her own race; and Mr. Alex. Harvey,[77] in developing a theory of Mr. McGillivray, has supposed that the embryo, whilst in utero, subjected the mother, by some sort of inoculation, to organic or dynamic modifications, the elements of which had been transmitted to the embryo by the father, and the mother would then retain the impress permanently. In support of this hypothesis, the author reminds us that certain diseases, such as old and non-contagious syphilis, may be communicated to the mother by the mediation of the fœtus. He further observes that in horses, oxen, sheep, and dogs, a female, impregnated for the first time by a male, may for a long time preserve a certain disposition to produce with another male young resembling the first, a phenomenon well-known to breeders. He finally remarks that a mare, having given birth to a mule, conceives subsequently with greater difficulty from horses than from asses, and he connects these instances with those of the native women who once impregnated by a white man, become by it barren in their connexion with men of their own race without, however, losing the capacity of becoming again pregnant by white men. I cannot accept this adventurous theory which Dr. Carpenter was nearly ready to adopt, but which he has discarded in a postscript, owing to fresh information which he received while his article went to press.[78] The influence of the first male upon the succeeding progeny has been many times rendered evident by the crossing of animals of the same race, and even of different species.[79] The existence of such a phenomenon in the human species is, at any rate, still doubtful, and the connexion of facts of this kind, with Strzelecki’s assertion, is yet more questionable. We must also observe that Strzelecki, in pointing out the barrenness of savage women who have cohabited with the Whites, does not merely speak of such who have produced Mulattoes, but applies equally to those women who had not given birth to any children; and if Mr. Harvey had taken the exact meaning of the text, he might, perhaps, not have advanced his theory.