June, 1941] 



Animal Breeding and Nutrition 



IS 



Here the analogy ceases because the functions of the body are far 

 more numerous and complicated than those of any mechanical de- 

 vice. For example, everyone knows that this biological engine can- 

 not be started again if it is stopped. Hence the significant charac- 

 teristic of the muscle cells is their constant activity, flexing and 

 contracting rhythmically w^hether the individual is asleep or av^ake. 

 They are oxidizing stored food but when food is not available they 

 oxidize body substance to keep the process going, thus also produc- 

 ing heat. By this process the cell manifests the two characteristic 

 expressions (motion and the production of heat) which we accept as 

 evidence of life. 



FIGURE 10. KliVhLAiiuJN, A DRAFT TYPE CliAAiiiUiN OF THE INTERNATIONAL 



LIVESTOCK EXPOSITION AT CHICAGO 



He shows weight and power, slow action, smaller power plant, basal metabolism 8,800 cal- 

 ories. 



During usual conditions when an animal burns food, combustion 

 flares up temporarily with the result that the heat produced is much 

 in excess of that due to the organic (hormone) stimulus. Hence it 

 is the intensity of this internal organic urge conditioned by hormone 

 stimulus to keep life processes going in the absence of food that rep- 

 resents the genetic adaptation of the animal motor. 



The continuity of this self-expression of life processes by the pro- 

 toplasmic cells collectively, this conversion or utilization of energy, 

 is metabolism. When the body is relaxed and not actively digesting 



