This section is from the book "The Transmission Of Life. Counsels On The Nature And Hygiene Of The Masculine Function", by George H. Napheys. Also available from Amazon: The Transmission of Life.
If there exists in nature, and that there does is abundantly proved, a law by which the offspring so strongly tend, as we have just been endeavoring to show, to inherit the physical, mental, and moral natures of their parent, how does it happen that there are so many exceptions to be noted ? In other words, what are the causes of non-inheritance ?
We have already mentioned a number, to which we need now only allude. One of these is atavism, i. e., resemblance to remote instead of immediate ancestors. This agency we have sufficiently explained. Another is the neutralizing effect of the qualities of one parent over the other in their mutual transmission to the child. In this manner, a third being may be produced, unlike either parent. A third cause is the overpowering influence of hostile circumstances and unfavorable conditions of life. As is very aptly remarked by Mr. Darwin, in considering animals and plants under domestication, " no one would expect that our improved pigs, if forced during several generations to travel about and root in the ground for their own subsistence, would transmit, as truly as they now do, their tendency to fatten, and their short muzzles and legs. Dray horses assuredly would not long transmit their great size and massive limbs, if compelled to live in a cold, damp, mountainous region; we have, indeed evidence of such deterioration in the horses which have run wild in the Falkland Islands. European dogs in India often fail to transmit their character. Sheep in tropical countries lose their wool in a few generations."
A fourth check to inheritance is to be found in what is known as the " law of diversity." In obedience to this law children differ from their parents and from each other. This so-called law is, however, merely an illustration of the strength of inheritance, for its effects are due to the transmission of temporary and accidental conditions in the parents. There is always under such circumstances a strong inclination in future generations to depart from the modifications thus accidentally produced, and to return to the original type.
There are two potent influences affecting the character of the child to which we have made no allusion. We refer to the power of the mother's imagination over the physical and mental condition of her unborn infant, and to the influence of the mother's mind on the child at her breast. These subjects have been elsewhere discussed in treating of the physical life of woman.
We do not think it worth while to "point a moral" by applying the facts and principles we have now recorded about inheritance, to the life of the parents. Every intelligent reader can do this for himself.
Nor is it our purpose to prosecute the study of the formation of the child through the habits of the father beyond what we have already done.
From the first it has been our aim to impress upon our readers the momentous truth that the well-being of the generations to come, and consequently the destiny of races and nations, are closely dependent on the healthy condition of the male in his sexual relations. We have now traced these relations in the individual, and pointed out their hygienic laws, from the period when they are first manifested to their final effects on the offspring.