AND PERSONALITY 



Although the ass has for a long time been adapted to a 

 warm climate, the size of the energy system of the ass has 

 not been adapted to the production of large amounts of 

 heat for maintaining the warm-blooded state, as in the 

 case of the Shetland pony. Therefore, this low-geared pack 

 horse of the tropics and subtropics, like the burro, requires 

 much less food than the northern Shetland pony of equal 

 size. 



Relevant to this statement, it must be borne in mind that 

 the master of the lazy ass is correspondingly lazy and corre- 

 spondingly requires less food, whereas the master of the 

 active Shetland pony is subject to the same adaptation 

 against cold as the Shetland pony and, therefore, requires 

 a correspondingly larger amount of food. The cold Shetland 

 pony and his vigorous master can, of course, perform a 

 greater amount of service than can the warm, lethargic 

 ass and his lethargic master. 



The subarctic-adapted Shetland pony and the subtropic- 

 adapted ass are not the only members of the horse family 

 at our disposal for analysis of the energy-controlling system. 

 The remaining member of the horse family has not been 

 modified by man. This animal is the African zebra. 



The Zebra 



The zebra is adapted to the tropics and the subtropics. 

 The zebra possesses keen senses and great speed and is so 

 high-tempered that man has found it difficult to tame. 



An analysis of the energy-controlling systems of the ass, 

 the Shetland pony, and the zebra, with respect to the sizes 

 of their brains, hearts, and thyroid and adrenal glands, is 

 given below. 



143 



