HEREDITY 143 



of energy it can develop either in tractive power for'pull- 

 ing heavy loads or in the form of speed or graceful action 

 for the pleasure of the owner. Other animals are main- 

 tained in a state of domestication for other values of 

 various kinds which contribute to the food, clothing or 

 pleasure of man. In a sense the producer of live-stock 

 may be compared to a manufacturer who employs capital, 

 labor, raw materials and efficient- machines for the pro- 

 duction of more desirable and concentrated products. 

 In this comparison the raw materials are the grain, hay 

 and grass ; and the efficient machine is the animal. The 

 farmer's success and the interests of the consumer as 

 well are greatly dependent upon the efficiency of this 

 animal machine. Can Mendel's law be utilized in the 

 efforts of the breeder to increase the efficiency of animals ? 

 If so, what does the breeder need to know in order to 

 utilize the law of Mendel in further enhancing the value 

 of the prevailing types of domestic animals ? 



137. The complexity of animal characters. It must 

 be recognized in the beginning that the qualities which 

 are commonly mentioned by the breeder as highly desir- 

 able are generally the result of a combination of many 

 characters. These combinations do not behave as simple 

 unit characters. One of the first steps in the application 

 of Mendel's hypothesis to practical breeding must be to 

 analyze the valuable qualities of animals and determine 

 as far as possible the unit characters. It is probably 

 true that some combinations will behave in transmission 

 in the same manner as simple unit characters. But if 

 there are complex characters which behave in this manner 

 they must be determined by careful investigation. When 

 the qualities of an animal have been differentiated and 

 their behavior, in transmission determined, then the prac- 



