18 SOUTHERN rORK PRODUCTION 



Laws of breeding. — From time to time we read or hear 

 of the laws of breeding. The farmer or swine breeder 

 desires to know if he can make use of these to further his 

 interests. It is certainly well for the breeder to know 

 what progress has been made in the science of breeding, 

 but if it is something very practical desired the breeder 

 had best study the influence of environment, the origin, 

 history and pedigree of his animals, and make special 

 effort toward breeding more prolific strains than to 

 trouble about infection, saturation, maternal impressions 

 and the transmission of acquired characters. 



Heredity. — Heredity embodies those characteristics 

 which an individual acquires from its parents through its 

 germ plasm. The laws of hereditj^ are none too well 

 understood, but it is so universal in its application and 

 has been the basis of our breeding operations until we 

 have accepted it as a fundamental. Like begets like has 

 been the basis of all of our improvement in breeding. 

 Unfortunately, good and bad characteristics are cquallv 

 transmitted, when taken as a whole. Difficulty is ex- 

 perienced in placing a quantitative value on heredity. 



In the case of some characters we can measure the 

 character accurately, but the animal docs not necessarily 

 transmit those characters of its body, or somatic char- 

 acter, by means of its germ plasm, which we must recog- 

 nize as the sole carrier of hereditary substance. Weis- 

 mann, a famous investigator, has shown that the re- 

 productive cells are entirely distinct and separate from 

 the body or somatic cells. The germinal cells alone are 

 the carriers of the hereditary substances, and since these 

 are formed long before the birth of the animal, the im- 

 possibility of inheritance of acquired characters is evident. 



