EXTRACTIVE MATTERS. ,33 



C. The alcohol-extract contains : 



a. Constituenfs predpitable by tannic acid: 



{a) A matter precipitable by basic acetate of lead^ and 

 bichloride of mercury, but not by neutral acetate 

 of lead. 

 {b) A matter precipitable by basic acetate of lead, and 

 by an excess of bichloride of mercury, but not 

 by neutral acetate of lead : it is crj^stalline. 

 j3. Constituents not precipitable by tannic acid : 



(c) A matter precipitable by basic acetate of lead, but 

 not by neutral acetate of lead, or bichloride 

 of mercury. 



The substances Aa, Ab, Ba, &c., must be regarded as 

 the proximate constituents of the three groups of extractive 

 matters. 



We shall arrange them in two classes, according as they are 

 or are not precipitable by tannin. 



Constituents of the extract of flesh, precipitable by tannin. 



Aa exists in very small quantity in the water-extract : 

 it may be distinguished from the protein-compounds by its 

 indifference towards ferrocyanide of potassium ; from pepsin and 

 pyin, by its indifference to dilute acids; and from chondrin and 

 glutin by its aqueous solution, not gelatinizing on cooling. 



Kb may be distinguished in the same manner as Ka, 

 from the protein-compounds, pepsin, &c.i It differs from Aa 

 in being precipitated by protochloride of tin. "When isolated 

 it is tolerably soluble in alcohol, although that fluid will not 

 extract it directly from the water-extract. 



Ba occurs in minute quantity in the spirit-extract'. It 

 may be distinguished from the preceding compounds by its 

 solubility in spirit, and by its reaction with the acetates of 

 lead. 



These three substances, Aa, Kb, and Ba, differ so slightly in 

 their reactions with various tests, that we may conclude that 

 in all probability they are merely modifications of one and the 

 same matter. 



' The same observation applies equally to all the following constituents of extractive 

 matter. 



