CHEMICAL BASIS OF THE ANIMAL BODY. 43 



disappears on warming and comes down again on cooling. If excess 

 of the salt is added the precipitate does not dissolve on warming. 



2. Add carefully a few drops of pure nitric acid ; a precipitate is 

 formed if the acid is not in excess, which disappears on warming and 

 comes again on cooling. 



3. Add acetic acid, avoiding all excess, and then a trace of 

 potassium f errocyanide ; a precipitate is formed which disappears on 

 warming and reappears on cooling. 



4. On the addition of caustic soda in excess and a trace of sulphate 

 of copper the ordinary biuret reaction is obtained. This reaction 

 distinguishes hemialbumose from other soluble proteids, with the 

 exception of peptones. 



Hemialbumose has so far been spoken of as being one uniform 

 substance only. Kiihne and Chittenden in their earlier work 1 at first 

 distinguished merely between a soluble and insoluble form ; more 

 recently they have described four closely allied, but distinct forms 

 of the albumose 2 . (1) Protalbumose. Soluble in hot and cold water 

 and precipitable by NaCl in excess. (2) Deuteroalbumose. Soluble 

 in water, not precipitated by NaCl in excess, unless an acid be added 

 at the same time. (3) Heteroalbumose. Insoluble in hot or cold 

 water; soluble in dilute or more concentrated solutions of sodium 

 chloride, and precipitable from these by excess of the salt. (4) Dys- 

 albumose. Same as heteroalbumose, except that it is insoluble in salt 

 solutions 3 . Hemialbumose as ordinarily prepared may hence be re- 

 garded as a mixture of these several albumoses in varying proportions 

 according to the conditions of its preparation. 



The preceding statements as to the. existence of four forms of hemi- 

 albumose are however contested by Herth, Straub and Hamburger 

 (loc. cit. on p. 41). 



The peptones. Recent work has shewn that in all probability 

 the various substances which have been described as peptones have 

 consisted to some extent, if not largely, of a mixture of true peptones 

 with variable quantities of albumoses. Our knowledge of the nature 

 and properties of true peptones is at present in a state of transition, 

 so that it is on the whole advisable to give some account of the older 

 work as well as of the more recent. 



1 Zt.f. Biol. Bd. xix. (1883), T. 174. 



2 Ibid. Bd. xx. (1884), S. 11. 



3 For further details the original papers of Kiihne and Chittenden must be 

 consulted, more especially Zt. f. Biol. Bd. xx. (1884), S. 11. See also Neumeister, 

 Zt.f. Biol. Bde. xxm. (1887), S. 381; xxiv. (1888), S. 267; xxvi. S. 324. The 

 preparation and separation of the albumoses is conveniently given in Kohmann's 

 " Anleitung zum chemischen Arbeiten." Berlin, 1890, S. 48. 



