422 CONNECTIVE TISSUE IN MUSCLE. 



readily detected by adding an excess of acetic acid to the filtered 

 alkaline fluid. The proteids present in the latter are redis- 

 solved by this procedure, while the mucin is precipitated in 

 flocks." Again, in reference to the final alkaline fluid obtained 

 after the treatment with the more dilute alkali, it is stated : 

 " There may still be present a small quantity of mucin, which 

 is readily removed by adding acetic acid in excess and filtering 

 off the precipitate formed after some time ; fatty acids are also 

 retained on the filter." * 



Although we have been unable to find any reference to the 

 occurrence of mucin in muscles, it did not seem improbable 

 that this compound proteid might be present ; for mucin is a 

 characteristic component of white fibrous connective tissue, 

 and apparently also of bone.f We have therefore separated 

 the connective tissue from muscle and isolated the so-called 

 mucin described by Schepilewsky. Three different samples of 

 muscular tissue were examined, two of which were lean beef, 

 the third being rabbit's muscle. In each instance about five 

 hundred grams of the meat were chopped up, rubbed in a 

 mortar repeatedly with water and strained, until practically all 

 of the muscle fibres were eliminated. The connective tissue 

 residue was then placed in five per cent sodium hydroxide so- 

 lution for about fifteen hours. The resulting extract was 

 strained off and filtered ; the filtrate was acidified with acetic 

 acid and the flocculent precipitate obtained was washed thor- 

 oughly with water by decantation, with alcohol and ether, and 

 dried at 105 C. This was preparation A, which might be 

 made up in part or entirely of mucin, as the latter is readily 

 soluble in alkalies, but insoluble in excess of acid. The residue 

 undissolved after treatment with the caustic alkali was treated 

 with half per cent sodium hydroxide solution, in which the 

 collagenous tissue dissolved together with some saponified fats. 

 The solution was filtered and acidified with an excess of acetic 

 acid, which threw down a precipitate of proteid and fatty 

 acids. This precipitate would not dissolve completely in a 



Schepilewsky, loc. cit, pp. 367-358. 



t Gies, Amer. Jour. Physiol., 1900, iii, p. rii. 



