CHAPTER XVI 

 ANIMAL MOTORS 



399. The animal as a motor. Although the animal dif- 

 fers from other forms of motors, being an animated thing, 

 it is possible, however, to consider it as a machine in 

 which energy in the form of food is transformed into me- 

 chanical energy, which may be applied to the operation 

 of various machines. The animal as a motor is excep- 

 tionally interesting to those who have made a study of the 

 transformation of heat energy into mechanical energy, 

 for this is really what takes place. Combustible matter 

 in the form of grain and other foods is consumed with the 

 resultant production of carbon dioxide or other products 

 of combustion in various degrees of oxidation, and, as 

 stated before, mechanical energy is made available by 

 a process not clearly understood. 



Viewed from the standpoint of a machine, the animal 

 is a wonderful mechanism. Not only is it self-feeding, 

 self-controlling, self-maintaining and self-reproducing, 

 but at the same time is a very efficient motor. While the 

 horse is like heat engines in requiring carbonaceous fuel, 

 oxygen, and water for use in developing energy, it is 

 necessary that combustion take place in the animal body 

 at a much lower temperature than is possible in the heat 

 engine, and a much smaller proportion of the fuel value 

 is lost in the form of heat while the work is being done. 

 The animal is the only prime mover in which combustion 

 takes place at the ordinary temperature of 98 F. For 

 this reason the animal is one of the most efficient of prime 



