Physiology of the Metabolic Phenomena 



of the Body. 



BY the term metabolism are meant all those phenomena, whereby all 

 even the most lowly living organisms are capable of incorporating 

 the substances obtained from their food into their tissues, and making 

 them an integral part of their own bodies. This part of the process 

 is known as assimilation. Further, the organism in virtue of its meta- 

 bolism forms a store of potential energy, which it can transform into 

 kinetic energy, and which, in the higher animals at least, appears most 

 obvious in the form of muscular work and heat. The changes of 

 the constituents of the tissues, by which these transformations of the 

 potential energy are accompanied, result in the formation of excretory 

 products, which is another part of the process of metabolism. The 

 normal metabolism requires the supply of food quantitatively and 

 qualitatively of the proper kind, the laying up of this food within the 

 body, a regular chemical transformation of the tissues, and the pre- 

 paration of the effete products which have to be given out through the 

 excretory organs. 



229. General View of the most Important 

 Substances used as Food. 



Water. 



When we remember that 5 8 '5 per cent, of the body consists of 

 water, that water is being continually given off by the urine and faeces, 

 as well as through the skin and lungs, that the processes of digestion 

 and absorption require water for the solution of most of the substances 

 used as food, and that numerous substances excreted from the body 

 require water for their solution e.g., in the urine, the great importance 

 of water and its continual renewal within the organism are at once 

 apparent. As put by Hoppe-Seyler, all organisms live in water, and 

 even in running-water, a saying which ranks with the old saying 

 " Corpora non agunt nisi fluida." 



Water as far as it is not a constituent of all fluid foods occurs in 



