An analysis of the case of a child shuddering at the sight of peaches is of interest in this connection. The child showed the greatest aversion to peaches, particularly to the fuzzy covering. The mother’s explanation was that peaches were unusually plentiful the year the child was born and that she had worked hour after hour at peeling and canning peaches shortly before his birth until she had become thoroughly sick of them. This acquired aversion on her part she believed had been transferred to the child. A few questions revealed the fact, however, that the mother, herself, had never liked peaches and when asked if they were distasteful to any other member of her own family she exclaimed, “Oh, yes, my mother would shudder and shake if a peach were brought near her.” And there we have it. The idiosyncrasy was an inherited one as many similar peculiarities are. The mental impression produced in the mother by her own experience with peaches had nothing to do with its occurrence in the child.

Very frequently also one encounters the mother who is sure she has engendered musical ability in her child by constant practise and study of music during pregnancy. The child is musical; what better evidence does one want! It seems never to occur to such a mother that the child is musically inclined because she herself is, as is evinced by her own desire in the matter even if she is not a skillful performer.

When we take into account the extreme credulity of many people, the unconscious tendency of mankind to give a dramatic interpretation to events where causes are not certainly known, the hosts of coincidences that occur in life, and the multitude of cases where something should happen but nothing does, we are compelled to believe that the whole matter of direct specific influence of the mother’s mind on the developing fetus is a myth. After seeing the conditions which prevail in Mendelism, for example, it will take strong faith to believe that a mother with duplex brown eyes can “think” or “will” blue eyes on her baby, yet this would be a mild procedure compared to some we are asked to accept by believers in the transmission of maternal impressions. Most of all, however, when we recall the actual relation between the embryo and the mother—a narrow umbilical cord is the sole means of communication between the two—the physical impossibility of a connection between some particular mental happening of the mother and a corresponding specific modification in the fetus becomes evident. For there are no nerves in the umbilical cord, the only path of communication between mother and fetus being the indirect one by way of the blood stream. Even this method of communication is limited inasmuch as the mother’s blood does not circulate through the blood vessels of the fetus. Gaseous and dissolved substances are merely interchanged through the thin walls of the capillary blood vessels in the placenta.

Injurious Prenatal Influences.—However, the denial that a particular mental impression of the mother is associated with a particular structural defect in a child does not carry with it the implication that prenatal influences of all kinds are negligible factors. On the contrary any deleterious effect which can reach the fetus through absorption from the blood of the mother may be of grave consequence. There is not the least doubt that malnutrition or serious ill-health on the part of the mother often has a prejudicial effect on the unborn offspring. Severe shock or grief, worry, nervous exhaustion, the influence of certain diseases, poisons in the blood or tissues of the parent, such as lead, mercury, phosphorus, alcohol and the like, may all act detrimentally, but they operate either by rendering nutrition defective, by direct poisoning, or by generating toxins in the blood of the parent which then poison the fetus. Among the latter may be mentioned the toxic products of tuberculosis and certain other bacterial diseases. Such factors operating on the unborn young or even on the germ-cells may cause malformations, arrests of development, instabilities of the nervous system, and general physical or mental weakness. The effects are general, however, and not specific.

To distinguish certain of these prenatal effects, particularly those of certain diseases or poisons, from true hereditary influences they are frequently spoken of as cases of transmission rather than inheritance from parents. Some writers use the technical term blastophthoria, or false-heredity, extending the meaning so as to include also any damage that might be inflicted on the germ-cells.

Lead Poisoning.—By way of illustration of how certain cumulative poisons may act we may examine a tabulation of eighty-one cases of lead poisoning as reported by Constantin Paul (Fig. 29, [p. 164]).

The table requires little comment. The disastrous effects of such poisoning are apparent in every class of cases. The sixth class where the husband alone was exposed to lead shows that the poison can operate directly through the germ-cell. Other observers note that in the children of workers in lead, there is a distressing frequency of feeble-mindedness and epilepsy.

That lead poisoning operating through the germ-cells of the father can affect the development of the young harmfully is well shown in Fig. 30, [p. 165], which is a photograph of two young rabbits from the same litter The white young one is from a normal albino mother mated to an albino father which had received lead treatment. The pigmented young one is from the same albino mother by a normal pigmented father. Although the white father was considerably larger than the pigmented father, nevertheless the young of the former, because of the harmful effects of the lead, is distinctly smaller and less lively. A number of litters, each from the same mother but in part from a lead-poisoned father and in part from a normal father, have been secured. All show more or less the same results. The experiments are still in progress in the department of experimental breeding at the University of Wisconsin.

Number
of
cases.		Number
of
pregnancies.		Abortions,
premature
labor, and
stillbirths.		Infants
born
living.		Remarks.
1.Mother showing symptoms
of plubism		415132One infant died
within 24 hours.
2.Mother working in type
foundry, all of whose
previous pregnancies had
been normal		536297Four of these died
in first year.
3.Mother who during period
of work in type foundry
had five pregnancies		1550After ceasing to
work had
healthy child.
4.Mother working intermittently
in type foundry; while
working there		3330When away from
work for some
period of time
gave birth to
healthy children.
5.Mother in whom blue line
on gum the only sign of
lead poisoning		629218
6.Husband alone exposed to
lead		?321220Of these, eight
died in first year,
four in second,
five in third.

Fig. 29