70 PRINCIPLES OF PHYSIOLOGY 



higher complexity may yet be formed. It 

 is not easy to give examples of syntheses in the 

 animal body. If benzoic acid is given in 

 food or as a drug, it unites with glycine, 

 probably in the liver, to form hippuric acid, 

 with the elimination of a molecule of water 

 Many organic acids may thus be built up. 

 Thus aromatic bodies unite with sulphuric 

 acid, and conjugated sulpho-acids thus formed 

 are eliminated by the kidneys. No doubt 

 synthetic processes may also build up fatty 

 phosphorized substances existing in nervous 

 matter, haemoglobin (the colouring matter of 

 the red corpuscles), and even proteins. 



(C) Enzyme or Ferment Action. One of the 

 most interesting chapters in the history of 

 scientific discovery has been that of the 

 nature of fermentation. Fermentation and 

 putrefaction have been known from early times, 

 but their true nature has been discovered only in 

 comparatively recent years. It is now known 

 that both are connected with the life-history 

 of micro-organisms, such as in the ordinary 

 fermentation of sugar into alcohol, carbonic 

 acid, and other substances, by the agency of 



