2i 4 THE HUMAN SPECIES 



50 in man) death occurs rapidly from coagulation of the cell 

 albumins. 1 The conversion of heat into capacity for work is 

 subject to the law of conservation of energy no less in the 

 animal organism than in non-living matter. Helmholtz has 

 calculated that with his muscles man is able to perform an 

 amount of mechanical work equivalent to a fifth part of the 

 total power produced by the chemical energy in the whole 

 body in the same period of time ; in the horse the ratio of 

 mechanical (external) work to the chemical energy is only one 

 quarter.- 



Finally, we have to consider the production of certain 

 sounds by the respiratory mechanism, some of which only 

 occur in man, some in other animals ; part of them voluntary, 

 part involuntary. (Other variations in the movements of 

 respiration will fall under the heading of " Expression of the 

 Emotions".) 



The power of voluntarily clearing the throat of mucus, 

 " hawking," is peculiar to man, although closely allied to it is 

 the involuntary "coughing" of man, horses, sheep, goats arid 

 dogs ; while the sound of the ape's cough is scarcely distinguish- 

 able from that of man's. 



" Sneezing " occurs in sheep dogs and cats as well as in man. 

 " Yawning " with a short deep inspiration and forcible expiration 

 is quite as pronounced in dogs as in man. 



" Snorting " is an accomplishment we share with dogs and 

 pigs, while all animals are capable of " sniffing," a device con- 

 sisting of a quick succession of short inspirations which im- 

 proves the olfactory perceptions. 



V. Intestinal System. 



In order to maintain the equilibrium of the body, man and 

 all animals have to replace the waste of solid and fluid 

 constituents by eating and drinking. Animals that feed ex- 

 clusively on flesh (carnivora) require very large amounts of 

 meat to maintain the .body-weight and smaller amounts of fat 

 and carbohydrate. In herbivora, the protein consumed in 



1 Ranke, he. cit., i., p. 348. 



2 Tereg in Ellenberger's Physiologic, ii., p. 66. 



