258 MUCIN. [BOOK i. 



cipitate which at first appears granular, but afterwards flocculent. 

 The precipitated body may be collected on a filter, and washed with 

 water or dilute alcohol. 



(b) From bile. As bile often contains very large quantities of 

 mucin, it may serve as raw material for its preparation. The 

 bile is treated with its own volume of 80 p.c. alcohol, which throws 

 down a precipitate composed of mucin mixed with epithelium, 

 proteids, &c. The precipitate is separated by decantation and washed 

 with fresh alcohol, it is then suspended in a large quantity of 

 lime-water; after some days the solution is decanted and precipi- 

 tated with acetic acid, the precipitate is washed successively with 

 water, alcohol and ether 1 . This method may with slight modifica- 

 tions be employed to separate mucin from sputum, or other liquids 

 containing the body. In the case of sputum it would be well 

 to follow Gautier's advice, to commence by washing with water 

 acidulated with acetic acid. 



Properties Mucin when freshly precipitated is a glutinous 



of mucin. substance, which forms with water an opaque liquid 



in which it is held in suspension without being dissolved. It is 

 soluble in weak solutions of the alkalies and alkaline earths, 

 from which it is precipitated by dilute acids, acetic acid being usually 

 employed for this purpose. 



It is insoluble in dilute hydrochloric acid, containing from 01 

 to 1 p.c. of real acid ; but it is soluble in hydrochloric acid of 5 p.c. 



Mucin which has been precipitated by acids is insoluble in 

 solutions of common salt. 



Mucin is not digested by artificial gastric juice ; it is dissolved by 

 alkaline solutions of trypsin. 



Mucin is precipitated by acetate of lead from neutral or weakly 

 alkaline solutions, but by no other metallic salts. It is not pre- 

 cipitated by acetic acid and potassium ferrocyanide : it is also 

 unaffected by tannic acid. 



When treated with copper sulphate and caustic potash it prevents the 

 precipitation of cupric hydrate ; the solution is not reduced on boiling. 



When boiled with Millon's reagent, mucin gives a rose colouration. 

 Elementary Mucin contains the elements C, H, N, 0, but no 

 composition sulphur. The following are the results of elementary 

 analyses by various investigators. 



I. (Scherer). H. (Obolensky). III. (Eichwald). 



Mucin from Mucin from Mucin from 



mucous con- submaxillary Helix pomatia. . 



tents of a cyst. gland. 



Carbon 5217 52'31 48'94 



Hydrogen 7'01 7'22 6'81 



Nitrogen 1264 11'84 8'50 



Oxygen 2818 2863 35'38 



1 Gautier, Chimie appliquee a la M6decine, Vol. n. p. 126. 



