156 MANURE. 



Bone itself is allied to protein by its cartilage 

 which composes nearly one-third the weight, and 

 which boiling water, under pressure, completely ex- 

 tracts in the form of gelatin, or glue. 



219. All these varied forms of protein may be 

 tabulated so as to express at a glance, their rela 

 tion to each other, if these elements, Carbon, Hy- 

 drogen, Nitrogen, and Oxygen, are expressed by 

 C. H. N. O., and to each is added figures, which 

 represent the number of atoms, entering into the 

 compound. This is called chemical notation, and 

 each set a chemical formula. 

 Protein, 



Gelatin of tendons, 



Chondrin, or gelatin of cartilage, 



Compact horny matter, 



Feathers, 



But the great practical lesson, taught by this simi- 

 larity of constitution, is, that it enables the chemist to 

 present at one view, animal and vegetable substan- 

 ces, as carbon, water, ammonia, and carbureted hy- 

 drogen. This is the view which the farmer takes, 

 for he knows that these are the elements of manure. 

 Protein may be resolved into 



