CONSTITUENTS OF COTTON-FIBRE. 125 



Now^ as tyrosine is only formed^ as far as we know, from 

 albumen and bodies of the same class, it is almost certain 

 that cotton contains a small quantity of an albuminous 

 substance. The oxalic acid obtained in this experiment 

 was doubtless derived from the pectic acid. Of the ratio 

 in which the latter stands to the albuminous matter, some 

 estimate may be formed by that subsisting between their 

 respective products of decomposition. 



The precipitate produced by acid in an alkaline extract 

 of cotton contains, then, the following organic sub- 

 stances : — 



1. Cotton wax. 



2. Margaric acid. 



3. A colouring-matter easily soluble in alcohol. 



4. A colouring-matter sparingly soluble in alcohol. 



5. Pectic acid. 



6. Albuminous matter. 



Of these various bodies the pectic acid far exceeds the 

 others in quantity. Then follow the colouring-matters. 

 The three other constituents are present in extremely 

 minute quantities only. Now I am far from asserting 

 that cotton -fibre does not contain, besides these, other 

 organic substances which are soluble in water or alkali, 

 but are not afterwards precipitated by acid. Indeed it 

 is quite possible that such may be the case ; for it is well 

 known that cotton, during the process of bleaching, loses 

 about five per cent, of its weight, whereas the total weight 

 of all the substances obtained in my experiments amounts 

 to hardly one-half per cent. It is, however, not improbable 

 that a portion of the matter which escapes observation 

 when my mode of proceeding is adopted, may consist in 

 great part of parapectic acid. This body, though in- 

 soluble in tolerably strong acids or saline solutions, is 

 soluble in pure water. When, therefore, it is precipi- 

 tated from an alkaline solution, the precipitate, on being 



