724 MUG IN, GELATIN, ETC. [Apr. 



Mucin. (O, 35-75. H, 6-81. N, 8-50. C, 48-94.) 1 



The characteristic component of mucus. Its exact composition is 

 not yet known, the figures given above being merely an approximation. 



As occurring in the normal condition it gives to the fluids which 

 contain it the well-known ropy consistency, and can be precipitated 

 from these by acetic acid, alcohol, alum and mineral acids ; the latter, 

 if in excess, redissolve the precipitate, but this is not the case with 

 acetic acid. In its precipitated form it is insoluble in water, but swells 

 up strongly in it, and this effect is increased by the presence of many 

 alkali salts. Alkalis and alkaline earths dissolve it readily. Its 

 solutions do not dialyse ; they give the proteid reactions with Millon's 

 reagent and nitric acid, but not that with sulphate of copper, and are 

 precipitated by basic lead acetate only when neutral or faintly alkaline. 

 According to Eichwald 2 , when heated with dilute mineral acids, 

 inucin yields acid-albumin, and another body which in many of its 

 properties closely resembles a sugar, inasmuch as it reduces solutions 

 of cupric sulphate. Prolonged boiling with sulphuric acid gives leucin 

 and about 7 p. c. of tyrosin. 



Preparation*. Ox-gall or an aqueous extract of finely-chopped 

 submaxillary gland is acidulated with acetic acid; the precipitated 

 mucin is then washed with water, dissolved in dilute sodic carbonate 

 and finally precipitated with acetic acid. It may also be obtained from 

 snails 4 . 



Chondrin. (0, 31-04. H, 6-76. N, 13-87. C, 47-74. S, 

 60 p. c.) 5 



This is usually regarded as forming the essential part of the matrix 

 of hyaline cartilage, and is contained in the interstices of the fibres in 

 elastic cartilage. A similar substance can be prepared from the cornea. 

 Boiled with water, it dissolves slowly, forming an opalescent solution, 

 which is precipitated by acetic acid, lead acetate, dilute mineral acids, 

 alum, and salts of silver and copper ; an excess of the last four reagents 

 redissolves the precipitate. Solutions of this body gelatinise on 

 standing, even if very dilute; the solid mass is insoluble in cold 

 water, readily soluble in hot water, alkalis and ammonia. 



The aqueous and alkaline solutions of chondrin possess a left-handed 

 rotatory power on polarised light of 213-5; in presence of excess of 

 alkali this becomes - 552-0, both measured for yellow light 8 . 



1 Eichwald, Ann. d. Chem. u. Pharrn. Bd. 134, S. 193. 2 Op. cit. 



3 Eichwald, op. cit. and Chem. Centralb., 1866, No. 14. Staedeler, Ann. de Chem. 

 u. Pharm. Bd. Ill, S. 14. Landwehr, Zeitscli. f. physiol. Chem. Bd. v. (1881), 

 S. 371. 



4 Landwebr, Zeitsch. f. physiol. Chem. Bd. vi. (1882), S. 75. 

 8 I. v. Mering, Beitrag zur Chemie des Knorpels, 1873. 



8 Hoppe-Seyler, Hdb. phys. path. chem. Anal 4 Aufl. 1875, S, 262. 



