The conviction that a better knowledge of the principles of breeding would render our system of agriculture more profitable, and the hope of contributing somewhat to this end, have induced the attempt to set forth some of the physiological principles involved in the reproduction of domestic animals, or in other words, the laws which govern hereditary transmission.
[1] Local names for _lyery_, or black fleshed cattle.
The first and most important of the laws to be considered in this connection is that of SIMILARITY. It is by virtue of this law that the peculiar characters, qualities and properties of the parents, whether external or internal, good or bad, healthy or diseased, are transmitted to their offspring. This is one of the plainest and most certain of the laws of nature. Children resemble their parents, and they do so because these are hereditary. The law is constant. Within certain limits progeny always and every where resemble their parents. If this were not so, there would be no constancy of species, and a horse might beget a calf or a sow have a litter of puppies, which is never the case,--for in all time we find repeated in the offspring the structure, the instincts and all the general characteristics of the parents, and never those of another species. Such is the law of nature and hence the axiom that "like produces like." But while experience teaches the constancy of hereditary transmission, it teaches just as plainly that the constancy is not absolute and perfect, and this introduces us to another law, viz: that of variation, which will be considered by and by; our present concern is to ascertain what we can of the law of similarity.
The lesson which this law teaches might be stated in five words, to wit: _Breed only from the best_--but the teaching may be more impressive, and will more likely be heeded, if we understand the extent and scope of the law.
Facts in abundance show the hereditary tendency of physical, mental and moral qualities in men, and very few would hesitate to admit that the external form and general characteristics of parents descend to children in both the human and brute races; but not all are aware that this law reaches to such minute particulars as facts show to be the case.