186 QUARTERLY JOURNAL. 



Of the non-nitrogenized principles, there are some which are 

 composed of carbon united with oxygen and hydrogen, the two 

 latter elements existing precisely in the proportion for forming 

 water. They may, therefore, be considered as compounds of car- 

 bon with the elements of water, and are called neutral principles. 

 The most important of them are starch, gum, and the different 

 kinds of sugar. These substances differ from each other only in 

 the proportion of the elements of water contained in them. They 

 have been considered by some chemists as hydrates of carbon, but 

 this denomination is of questionable propriety, since it is by no 

 means generally admitted that water actually exists in them. 



There are other non-nitrogenized principles which are also com- 

 pounds of carbon with oxygen and hydrogen, but these latter ele- 

 ments are not in the proportion to form water, the hydrogen or 

 the oxygen being in excess. They are called non-neutral com- 

 pounds. The principal of them are fat, wax, acids, &c. 



The nitrogenized principles are albumen, fibrin and casein. They 

 all contain a substance called protein, consisting of carbon, oxygen, 

 hydrogen and nitrogen ; and this protein is combined with minute 

 proportions of sulphur and phosphorus. As regards their chemical 

 composition, they differ from each other only in the proportion of 

 sulphur and phosphorus combined with protein. They possess, 

 however, different properties, not depending merely on their che- 

 mical composition. 



There is a fourth nitrogenized principle called gelatine, found in 

 the bones and cellular tissue, which does not seem to be a com- 

 pound of protein. Its chemical constitution is still uncertain. 



The following table exhibits the proximate principles, and their 

 relation to each other : 





Non-nitrogenized 

 principles : 



["starch =12 carbon -f 10 water, 

 neutral, ' S^ni =12 carbon + 11 water, 



[ sugar = 12 carbon +11 water, 

 fat, 

 non neutral, { wax, 



l^ acids. 



! albumen = protein + S. + P. 

 fibrin = protein +2 S.+P. 

 casein = protein +S. 

 gelatine — chemical constitution doubtful. 



