ANIMAL BREEDING. The art, of breeding ani mals, as practiced at the present day, is found ed on the practice of the most successful breed ers, and its rules are almost exclusively empirical in their origin. They have not been worked out on the basis of scientific investigation and ex periment. but may be regarded rather as con tributions to science than deductions from it. Hence, while many interesting and instructive experiences and observations have been recorded, and these have been brought together and dis cussed in the light of the best knowledge avail able. comparatively few general principles have been deduced as yet. and many important points upon which it would be exceedingly valuable to have definite information remain in obscurity. The breeding of animals has not yet been placed upon the scientific basis that, thanks to syste matic investigation, many other lines of agri cultural practice now occupy.
Breeding has been practiced from the earliest times, the horse having apparently received more attention from the ancients than the other kinds of farm animals. The ancients evidently had some knowledge of the laws of heredity, al though much stress appears to have been laid upon the exercise of external influences as well. Up to the middle of the Eighteenth Century the theory that "like produces like," and the rule to "breed from the best," comprised what was ImONVII of the principles of breeding, but it is evident that the extended applications of these empirical expressions were not fully appreciated. The early breeders had no consistent system of selection—their standards of excellence were, in fact, constantly changing. so that the conception of the 'best' differed widely from time to time, and this prevented any very high development of the most valuable qualities. Soon after the middle of the Eighteenth Century, Robert Bake well, of England, originated a new system of breeding, based upon careful selection from a single variety or breed, and close breeding to develop certain desirable qualities. The cross ing of different breeds had previously been held to be the road to improvement. Ile believed that
the maxim. "like begets like," was not limited to the external or more obvious characteristics, hut extended to the minutest detail of the animal organism. He regarded the animals he worked with as plastic, and lie sought so to mold these plastic forms as "to give expression to his ideal conception of the qualities that constitute per fection." His work and teachings produced a very marked effect on the practice of breeding, and the following out of his theories by a long line of able breeders has given us many improved breeds of live stock, each adapted to special con ditions and purposes.
Our knowledge of the principles of breeding rests to-day upon the development and the more intelligent application of the old maxim that like produces like—i.e. upon the law of heredity. According to this law, every animal embodies the sum of the characters inherited from its parents and ancestors, and those acquired as a result of its environment. The animal "inherits an assemblage of peculiarities representing the aggregate of parental charac ters." thus presenting a composite of its ances tors, which has been likened to a composite photograph of a number of persons, containing traces of each individual, some hardly discern ible, but strongest along certain lines common to all. 'Miles has advanced the theory that while all the characters are directly transmitted, some may become dominant in the offspring, and thus determine its external form and general char acteristics, while others remain latent until the conditions finally become favorable to their de velopment in an offspring, when they in turn may become dominant, and thus obscure other characters. This theory has sonic degree of plausibility, and would account for many ap parent exceptions to the law of heredity. Those who do not accept it entirely hold that only such characters as have become fixed are trans mitted with certainty, and that the theoretical effect of the law of heredity is only realized or approximated in proportion as the 'ancestry has acquired a fixed and unvarying type.