140 NITROGENOUS SUBSTANCES. 



portance was ascribed to the bodies containing nitro- 

 gen, such as gluten, albumen, legumin, etc. 



a. These, and a number of others having a similar 

 character, have been classed together by some che- 

 mists under the name of protein bodies. They are, 

 in many cases, widely difTerent in form and proper- 

 ties, but all have about the same proportion of nitro- 

 gen, and the same general composition. 



6. As we come to examine the flesh, the blood, the 

 hair, and the organic part or gelatine of the bones, 

 we find that from all of them can be extracted various 

 substances that contain nitrogen. When these sub- 

 stances are subjected to chemical analysis, they are 

 proved to belong to the same class, and to have a 

 composition agreeing, with that of the nitrogenous or 

 nitrogen-containing bodies of the plant. 



This is a very striking fact, when we come to con- 

 sider its various bearings. The gluten of wheat, the 

 legumin of peas and beans, all the nitrogenous bodies 

 of the other grains and roots, are actually the same 

 thing as the nitrogenous bodies contained in the mus- 

 cle, the blood, the hair, the skin and the bones of the 

 animal. The plant, then, is a species of manufactory, 

 where food is prepared in such a form, that the ani- 

 mal can build up its own body with the least possible 

 trouble. These nitrogenous substances are carried 

 by the blood to each extremity of the frame, and are 

 deposited to fill up, supply, or enlarge every part, as 

 may be needed. The fact has long been established, 

 that our muscles, our hair, our skin, and even our 

 bones, are constantly undergoing a change. Some of 

 their particles are each day carried away, and rejected 

 from the body in various forms, their place being sup- 

 plied from the constituents of the food eaten. In this 

 way, particle by particle, the whole body is in time 

 renewed. 



When eating meat, we only eat a more concen- 



