Dr. Carpenter, the highest authority in Physiology, says "it has long been a prevalent idea that certain parts of the organism of the offspring" are derived from the male, and certain other parts from the female parent; and although no universal rule can be laid down upon this point, yet the independent observations which have been made by numerous practical breeders of domestic animals seem to establish that such a tendency has a real existence; the characters of the animal portion of the fabric being especially (but not exclusively) derived from the male parent, and those of the organic apparatus being in like manner derived from the female parent. The former will be chiefly manifested in the external appearance, in the general configuration of the head and limbs, in the organs of the senses (including the skin) and in the locomotive apparatus; whilst the latter show themselves in the size of the body (which is primarily determined by the development of the viscera contained in the trunk) and in the mode in "which the vital functions are performed."
On the whole it may be said that the evidence both from observation and the testimony of the best practical breeders goes to show that each parent usually contributes certain portions of the organization to the offspring, and that each has a modifying influence upon the other. Facts also show that the same parent does not always contribute the same portions, but that the order is reversed. Now, as no operation of nature is by accident, but by virtue of law, there must be fixed laws here, and there must also be, at times, certain influences at work to modify the action of these laws. Where animals are of distinct species, or of distinct breeds, transmission is usually found to be in accordance with the rule above indicated, i.e. the male gives mostly the outward form and locomotive system, and the female chiefly the interior system, constitution, &c. Where the parents are of the same breed, it appears that the portions contributed by each are governed in large measure by the condition of each in regard to age and vigor, or by virtue of individual potency or superiority of physical endowment.
This potency or power of transmission seems to be legitimately connected with high breeding, or the concentration of fixed qualities obtained by continued descent for many generations from such only as possess in the highest degree the qualities desired. On the other hand it must be admitted that there are exceptional cases not easily accounted for upon any theory, and it seems not improbable that in these the modifying influences may be such as to effect what may approximate a reconstruction or new combination of the elements, in a manner analogous to the chemical changes which we know take place in the constituents of vegetables, as for instance, we find that sugar, gum and starch, substances quite unlike in their appearance and uses, are yet formed from the same elements and in nearly or precisely the same proportions, by a chemistry which we have not yet fathomed. Whether this supposition be correct or not, there is little doubt that if we understood fully all the influences at work, and could estimate fairly all the data to judge from, we might predict with confidence what would be the characteristics of the progeny from any given union.
Practically, the knowledge obtained dictates in a most emphatic manner that every stock-grower use his utmost endeavor to obtain the services of the best sires; that is, the best for the end and purposes in view—that he depend chiefly on the sire for outward form and symmetry—that he select dams best calculated to develop the good qualities of the male, depending chiefly upon these for freedom from internal disease, for hardihood, constitution, and generally for all qualities dependent upon the vital or nutritive system.
The neglect which is too common, and especially in breeding horses, to the qualities of the dam, miserably old and inferior females being often employed, cannot be too strongly censured. In rearing valuable horses the dams are not of less consequence than the sires, although their influence upon the progeny be not the same. This is well understood and practiced upon by the Arab, who cultivates endurance and bottom. If his mare be of the true Kochlani breed he will part with her for no consideration whatever, while you can buy his stallion at a comparatively moderate price. The prevalent practice in England and America of cultivating speed in preference to other qualities, has led us to attach greater importance to the male, and the too common neglect of health, vigor, endurance and constitution in the mares has in thousands of cases entailed the loss of qualities not less valuable, and without which speed alone is of comparatively little worth.
FOOTNOTES:
[17] In his work, "De la Generation," Paris, 1828.
[18] Quoted, in part, from a paper by Alex. Harvey, M.D., read before the Medical Society of Southampton, June 6th, 1854.