B. Comparative Physiology and Psychology. 



i. Physiology. 

 General. 



THE elements of which the tissues of man and the Vertebrates 

 is composed are carbon, hydrogen, oxygen, nitrogen, sulphur, 

 phosphorus, chlorine, sodium, calcium, magnesium, iron and 

 minute traces of silicon and fluorine. 



The average amount of water contained in the tissues of an 

 adult man is 68 per cent. (Moleschott) ; the dry residue varies 

 (excluding contents of stomach and intestines) from 28 to 65 

 per cent., of which 23 to 65 per cent, is organic matter, and 2 

 to 5 per cent, inorganic. 



According to Dubois Reymond, plants form a fixed reduc- 

 ing apparatus with external roots which take from the air and 

 the earth certain inorganic substances, and yield them up to the 

 animal kingdom in organic form. Animals, on the other hand, 

 constitute an oxidation apparatus not fixed to the earth with 

 internal roots ; and they take the organic compounds from 

 plants and give back to the air and earth the inorganic material. 

 Animals consume proteids, carbohydrates, fat and oxygen, and 

 transform the chemical energy into vital forces, such as heat, 

 electricity and muscle contractility ; in these processes the 

 original substances are decomposed into CO 2 , H 2 O, and NH 3 , 

 so that the exchange of energy and matter goes on and no 

 atom is lost. " The weight of any new chemical compound 

 formed by combination, or decomposition, is always exactly 

 equal to the sum of the weights of the substances participating 

 in the process." 



Helmholtz has expressed very clearly the law of the con- 

 servation of energy : " Whenever free particles of matter move 



