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 *acterization and specification of the proteids required in the first place a knowledge of two particular compounds, the nucleins and the histones. This did not become possible until after the researches of Miescher and Kossel on the nucleins, which went on from 1874 to 1892, and those of Lilienfeld and d'Yvor Bang on the histones, from 1893 to 1899. The complete albuminoids are constituted by the combination of two kinds of substances—albumins or histones on the one hand, and nucleins on the other. By combining solutions of albumins or histones with solutions of nuclein, the synthesis of the proteid is effected. The study of the properties and characteristics of these nucleo-albumins and nucleo-histones is going on at the present moment. It is being carried out with much method and with wonderful patience by the German school.

All the proteids contain phosphorus in addition to the five chemical elements, carbon, oxygen, hydrogen, nitrogen, and sulphur, which are common to the other albuminoids. Another interesting feature in their history is that the action of the gastric juice divides them into their two constituents:—the nuclein, which is deposited and resists the destructive action of the digestive liquid, and the albumin or histone, which on the contrary experiences this action with the usual consequences. Thus the gastric juice furnishes a process which is very simple and very convenient in the analysis of the proteids.

Localization of the Nucleo-Proteids.—What we said before as to the important physiological rôle of the cellular nucleus may arouse the expectation that in it will be found the living matter which is chemically the most differentiated, the albuminoids of highest