MATTER AND ENERGY 69 



up varies directly as the pressure and inverse- 

 ly as the temperature. Thus, at the same 

 temperature, by lowering the pressure by 

 placing the oxy-haemoglobin in the partial 

 vacuum of an air pump, the compound 

 gives off the oxygen, without itself suffering 

 decomposition. When the pressure is raised, 

 the oxy-haemoglobin again takes up oxygen. 

 This process, known as dissociation, depends 

 on physical conditions. It plays an important 

 part in respiration. 



(5) By synthesis is meant the building up 

 of complex chemical substances by the union 

 of simpler bodies. This has been accomplished 

 by the chemist, and, as already stated, 

 numerous organic bodies have been formed 

 artificially in the laboratory, such are urea, 

 hippuric acid, glycine, taurin, creatin, glu- 

 cose, and numerous organic acids, such as 

 oxalic, lactic, succinic, benzoic, propionic, 

 acetic, and formic acids. Even bodies 

 resembling proteins have recently been 

 formed synthetically, and it is probable 

 that, by following out synthetic processes 

 that are suggested by theory, proteins of 



