HISTIDINE. 159 



the behavior of indol and skatol with the aromatic aldehydes have been 

 carried out by BLUMENTHAL. 1 



For the detection of indol and skatol in, and their preparation from, 

 faeces and putrefying mixtures, the main points of the usual method are 

 as follows: The mixture is distilled after acidifying with acetic acid; 

 the distillate is then treated with alkali (to combine with any phenols 

 which may be present) and again distilled. From this second distillate 

 the two bodies, after the addition of hydrochloric acid, are precipitated 

 by picric acid. The precipitated picrate is then distilled with ammonia. 

 The two bodies are obtained from the distillate by repeated shaking 

 with ether and evaporation of the several ethereal extracts. The residue, 

 containing indol and skatol, is dissolved in a very small quantity of 

 absolute alcohol and treated with 8-10 vols. of water. Skatol is precip- 

 itated, but not the indol. The further treatment necessary for their 

 separation and purification will be found in other works. 2 



Skatosine, CioHi 6 N 2 2 , is a base first obtained by BAUM in the pancreas auto- 

 digestion and later studied by SWAIN. It develops an indol- or skatol-like odor 

 on fusing with potassium hydroxide. LANGSTEIN 3 obtained a substance which is 

 perhaps identical with skatosine, in the very lengthy peptic digestion of blood 

 proteins. * 



Z-Histidine, C 6 H 9 N 3 02, is /3-imidazol-a-aminopropionic 4 

 CH-NHV 



C 



acid, =CH 2 



CH(NH 2 ) . 



COOH 



Histidine was first discovered by KOSSEL in the cleavage products 

 of sturine. It was found at the same time by HEDIN in the cleavage 

 products of proteins by acid hydrolysis, and by KUTSCHER among the 

 products of tryptic digestion, and finally also as a cleavage product of 

 many different animal and plant protein substances. It does not occur 

 in the protamines, with the exception of sturine. Of the protein bodies 

 globin (from horse-haemoglobin) seems to be richest in histidine, as 



1 Sasaki, Bioch. Zeitschr. 23, 29; Deniges, Compt. rend. soc. biol., 64; Blumenthal, 

 Bioch. Zeitschr., 19. 



2 For quantitative, colorimetric determinations of indol in feces see Einhorn and 

 Hiibner, Salkowski's Festschrift, Berlin, 1904; C. A. Herter and Foster, Journ. of 

 biol. Chem., 2. 



3 Baum, Hofmesister's Beitrage, 3; Swain, ibid.', Langstein, see Hofmeister, Ueber 

 Bau und Gruppierung der Eiweisskorper, in Ergebnisse der Physiologic, I, Abt. 1, 

 1902. 



4 See Pauly, Zeitschr. f. physiol. Chem., 42; Knoop and Windaus, Hofmeister's 

 Beitrage, 7 and 8; Knoop, ibid., 10; Ackermann, Zeitschr. f. physiol. Chem., 65. 



