286 Chemistry. [Lecture 34. 



the atmosphere, especially when acted upon by 

 the sun's rays so as to raise its temperature, it is 

 converted into vinegar. This entirely results 

 from the absorption of oxygen from the atmo- 

 sphere, by receiving a proper dose of which the 

 fluid becomes acetic acid. 



Putrefaction is a process more common to 

 animal than to vegetable substances, but it also 

 frequently takes place in the latter. As, how- 

 ever, ammonia is the general product of the pu- 

 trefactive process, it is evident that all vegetable 

 matter which undergoes it must contain nitrogen. 

 The process of putrefaction is not so well under- 

 stood as the vinous and acetous fermentations. 

 It is, in fact, the entire dissolution of the whole 

 body, in which new products are formed ; but the 

 principal circumstance seems to be that of the hy- 

 drogen and nitrogen combining together to form 

 ammonia, without which no putrefactive process 

 ever seems to take place. 



Animal Substances. 



The elementary principles of animal bodies 

 seem to be much the same as those of vegetables. 

 The compounds are less numerous. The sub- 

 stances usually found in the animal kingdom are 

 as follows : 



1. Gelatine. 5. Urea. 



2. Albumen. 6. Sugar. 



3. Fibrina. 7. Oils. 



4. Mucilage. 8. Resins. 



