52 THE MUCIN OF WHITE 



Undoubtedly, preliminary extraction of the tissue with salt 

 solution tends to remove a certain amount of proteid matter, 

 especially globulins, which might otherwise render the prod- 

 uct impure, and possibly this is in part the cause of the 

 lower content of carbon and nitrogen in Preparation No. 2 

 as contrasted with Preparation No. 1. Still there is no 

 certainty on this point, for it is to be remembered that pre- 

 cipitation of the mucin requires the addition of considerable 

 hydrochloric acid beyond neutralization of the alkaline fluid, 

 and this excess of acid would naturally exert" a marked solvent 

 action upon any albuminous matter present. That the first 

 lime-water extract is liable to yield a mucin with a higher 

 content of both carbon and nitrogen the results fully indicate, 

 and as a direct illustration of the difference in the content 

 of nitrogen in mucin obtained from a first and second extract, 

 we may instance the following experiment: Fifteen hundred 

 grams of tendons finely divided, as usual, were extracted 

 with 10 per cent salt solution for two days, then washed with 

 water and placed in three liters of half-saturated lime-water 

 for forty-eight hours. This first extract was then strained 

 off, and the tissue treated a second time with a like volume 

 of half-saturated lime-water, thus giving a second extract. 

 From the first extract, the mucin was precipitated by hy- 

 drochloric acid slightly above 0.2 per cent, the precipitate 

 washed with 0.2 per cent hydrochloric acid, then with water, 

 and lastly dissolved in 0.5 per cent sodium carbonate. From 

 this filtered solution a portion of the mucin was precipitated 

 by addition of 0.2 per cent hydrochloric acid, while a second 

 portion separated only on addition of a somewhat increased 

 strength of acid. These two fractions were washed thor- 

 oughly with 0.2 per cent acid, then with water, and finally 

 boiled with alcohol-ether until quite free from soluble matter. 

 The yield hi the first fraction was 1.4 grams, and in the 

 second fraction 1.0 gram. From the second lime-water ex- 

 tract the mucin was precipitated with 0.2 per cent hydro- 

 chloric acid, after which it was purified by washing with 

 0.2 per cent acid, solution in 0.5 per cent sodium carbonate, 



