METHODS OF ANALYSIS. 35 



In regard to the nutritive value of the albumoses and peptones 

 much uncertainty exists, but many investigators, as Munk, a Deiters, b 

 Zuntz, c Pollitzer, d and others, have shown that pure albumoses and 

 peptones can replace proteid matter of equivalent nitrogen content. 



The nature of the proteoses, as precipitated by saturating a sam- 

 ple of Liebig's meat extract with zinc sulphate, was lately investi- 

 gated by Micko, c who applied the Fischer ester method to the pro- 

 teoses. He identified the following amido bodies by this method: 

 •Glycocoll, leucin, isoleucin, alanin, amido valerianic acid, prolin (race- 

 mic and active), asparaginic acid (racemic and dextrorotatory), glu- 

 taminic acid anhydrid, and phenylalanin. No xanthin or kreatin 

 was found in the proteose precipitate. 



Gelatin, 

 general discussion. 



The addition of gelatin to meat preparations has been practiced 

 in the past. By this means the manufacturer increased or main- 

 tained a certain nitrogen content, but supplied the nitrogen in a 

 form lacking in stimulating effect and probably in nutritive value. 

 The buyer was consequently deprived of the characteristic essen- 

 tials of a true meat product, although the nitrogen content was 

 relatively high. In many cases only a small proportion of the added 

 gelatin existed in the extract as such, as it was converted by a grad- 

 ual process of hydration into gelatoses and gelatin peptones. While 

 the methods for the separation of gelatin from proteid matter are 

 far from satisfactory, it is a much simpler process than the detec- 

 tion of gelatoses and gelatin peptones and their separation from the 

 albumoses and peptones, no satisfactory method for the separation 

 of these bodies being known. 



Some gelatin may be formed in the preparation of a high-grade 

 extract of meat, although with proper precautions there should be 

 practically none present. When a sufficient amount of gelatin is 

 present it is readily detected by the setting qualities of the extract 

 after warming. The power of gelatinizing is only possessed by unal- 

 tered gelatin; its dissociation products do not have this power. 



Micko-f has recently studied the gelatin cleavage products and 

 finds that practically the same bodies are formed on hydrolysis as in 

 the case of the albumoses. In both cases glycocoll predominates. 

 This investigator states that no gelatin is present in Liebig's extract 



a Therap. Monatsh., June, 1888. Deutsche ined. Wochenschr. , 1889, No. 2. 



6 Von Noorden's Beitriige zur Lehre vom Stnffwechsel, 1892, p. 47. 



cAreh. gesam. Physiol., 1885, 57:313. 



d Ibid., p. 301. 



eZts. Nahr. Genussm., 1907, 7^:253. 



/Ibid., p. 284. 



