Thus, in the breeding of animals, if the object be to modify certain defects by using a male or female in which such defects may not exist, we cannot produce this desired alteration; or rather it cannot be equally produced in all the offspring, but can only be attained by weeding out those in whom the objectionable points are repeated. We are, however, of opinion that in the majority of instances, the hight in the human subject, and the size and _contour_ in animals, is influenced _much more by the male_ than the female parent--and on the other hand, that the constitution, the chest and vital organs, and the forehand generally more frequently follow the female."
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.