(5) in any case the phenomenon must be rare, for William Hunter could not find a coincidence between maternal impressions and foetal marks through a period of several years, and Bischoff found no case in 11,000 deliveries.  These statements embody the whole of the argument against maternal impressions, yet it is clear that they do not settle the matter.  Edgar, in a manual of obstetrics which is widely regarded as a standard work, states that this is “yet a mooted question."[193] Ballantyne, again, in a discussion of this influence at the Edinburgh Obstetrical Society, summarizing the result of a year’s inquiry, concluded that it is still “sub judice."[194] In a subsequent discussion of the question he has somewhat modified his opinion, and is inclined to deny that definite impressions on the pregnant woman’s mind can cause similar defects in the foetus; they are “accidental coincidences,” but he adds that a few of the cases are difficult to explain away.  At the same time he fully believes that prolonged and strongly marked mental states of the mother may affect the development of the foetus in her uterus, causing vascular and nutritive disturbances, irregularities of development, and idiocy.[195]

Whether and in how far mental impressions on the mother can produce definite mental and emotional disposition in the child is a special aspect of the question to which scarcely any inquiry has been devoted.  So distinguished a biologist as Mr. A.W.  Wallace has, however, called attention to this point, bringing forward evidence on the question and emphasizing the need of further investigation.  “Such transmission of mental influence,” he remarks, “will hardly be held to be impossible or even very improbable,” (A.W.  Wallace, “Prenatal Influences on Character,” Nature, August 24, 1893.)

It has already been pointed out that a large number of cases of foetal deformities, supposed to be due to maternal impressions, cannot possibly be so caused because the impression took place at a period when the development of the foetus must already have been decided.  In this connection, however, it must be noted that Dabney has observed a relationship between the time of supposed mental impressions and the nature of the actual defect which is of considerable significance as an argument in favor of the influence of mental impressions.  He tabulated 90 carefully reported cases from recent medical literature, and found that 21 of them were concerned with defects of structure of the lips and palate.  In all but 2 of these 21 the defect was referred to an impression occurring within the first three months of pregnancy.  This is an important point as showing that the assigned cause really falls within a period when a defect of development actually could produce the observed result, although the person reporting the cases was in many instances manifestly ignorant of the details of embryology and teratology.  There was no such preponderance of early impressions among the defects of skin and hair which might well, so far as development is concerned, have been caused at a later period; here, in 7 out of 15 cases, it was distinctly stated that the impression was made later than the fourth month.[196]