APPENDIX. 



ON THE CHEMICAL BASIS OF THE ANIMAL BODY. 



THE animal body, from a chemical point of view may be regarded 

 as a mixture of various representatives of three large classes of 

 chemical substances, viz. proteids, carbohydrates and fats, in associa- 

 tion with smaller quantities of various saline and other crystalline 

 bodies. By proteids are meant bodies containing carbon, oxygen, 

 hydrogen and nitrogen in a certain proportion, varying within narrow 

 limits, and having certain general features ; they are frequently spoken 

 of as albuminoids. By carbohydrates are meant starches and sugars 

 and their allies. We have also seen that the animal body may be 

 considered as an assemblage of protoplasm under various modifications 

 and of numerous products of protoplasmic activity. We do not at 

 present know anything definite about the molecular composition of 

 active living protoplasm ; but when we submit protoplasm to chemical 

 analysis, in which act it is killed, we always obtain from it a considerable 

 quantity of the material spoken of as proteid. And many authors go 

 so far as to speak of protoplasm as being purely proteid in nature : they 

 regard the living protoplasm as proteid material, which in passing from 

 death to life, has assumed certain characters and presumably has 

 been changed in construction, but still is proteid matter ; they some- 

 times speak of protoplasm as ' living proteid ' or ' living albumin.' It is 

 worthy of notice however that even simple forms of protoplasm, like that 

 constituting the body of a white corpuscle, forms of protoplasm which 

 we may fairly consider as native protoplasm, when they can be obtained 

 in sufficient quantity for chemical analysis, are found to contain some 



