TREATMENT. 126 



organic bodies, of which sugar and starch are the commonest 

 instances, and carbon the chief constituent. The presence 

 of water is necessary to sustain its power of exciting fer- 

 ment, and this is lost under pressure, or when the yeast is 

 desiccated and dried. 



It is alone its soluble part, however, that possesses the 

 property of inducing fermentation, and this only after it has 

 received oxygen from the atmosphere to which it must be 

 first exposed. It then developes in its mass carbonic acid. 

 Like vaccine or purulent matter — if not kept dry too long, 

 and under attendant circumstances which ensure its own 

 decomposition — when again moistened, it starts afresh on its 

 destructive mission. 



The fermenting process is easily carried forward to putre- 

 faction in bodies containing nitrogen, of which, in the animal 

 organism, blood is the primum mobile. And as nitrogen has 

 so low an affinity for the simple bodies, that it is said to be 

 in a state of indifference to them, its evolution is always 

 attended with an easy transposition of atoms. When acted 

 on by alkalies, by acids, or increase of temperature ; organic 

 compounds, containing nitrogen in the presence of water, 

 throw off all that element in the form of nitrates ; but if the 

 azotised animal matter first moistened, be exposed to the 

 action of the oxygen in the atmosphere ; then in the form of 

 ammonia. When gluten, the vegetable equivalent of albu- 

 men, is subject to the putrefactive process ; after the evolution 

 of carbonic acid and hydrogen commences, the ammonia 

 takes on its forms of phosphate, acetate, caseate and lactate, 

 which are produced in large quantities ; so that for the time 

 being the decomposition of the gluten ceases. But if water 

 is freshly added, the process is renewed, and then in addi- 

 tion to the products just mentioned, we have carbonate and 

 hydrosulphate of ammonia and a mucilaginous substance co- 

 agulable by chlorine, &c. Those who desire to follow the 

 labyrinthine changes of which nitrogen is capable, will find 

 that subject elaborately treated by Liebig,* from whom we 

 have freely taken the views above expressed. We must turn, 



* Ag, Chemistry, p 282, et seq. 



