Quite recently committees representing certain scientific bodies1 have recommended quite a different classification from the foregoing. The terms used in this classification are explained in the text which follows: 1 Am. Jour. Phys.t Vol. XXI.

Classification Of Proteins

The two classifications are given in this connection because much literature on nutrition recognizes the former, and the latter is now more or less in use. Certain differences should be noted. In the latter the term proteid is abandoned, and the term albuminoid is made to refer to the bodies classed as collagens or gelatinoids in the former grouping. Besides, the newer classification makes a more minute division of the proteins on the basis of constitution and characteristic properties.

42. The True Proteins

The proteins are the main and important nitrogen compounds either in the plant or in the animal. The nitrogenous bodies of seeds are little else than proteins, while young plants, and especially roots, such as beets and turnips, contain more nitrogen in the non-protein form. Proteins are the chief constituents of muscular tissue. Their chemical constitution is not definitely known. No investigator has yet been able to search out their manner of combination, but it is generally considered to be very complex, even to the extent of several thousand atoms. These bodies are constructed from the simpler ones of the inorganic world through the vital energies of plants, and they apparently must come to the animal fully organized.