CHEMICAL BASIS OF THE ANIMAL BODY. 881 



when heated with dilute mineral acids, mucin 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 per cent, of tyrosin. 



Preparation. 1 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. 2 



Chondrin. (0,31.04. H, 6.76. N, 13.87. 0,47.74. S, 0.60 per cent.) 3 



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 gelatinize on 

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

 soluble in hot water, alkalies, and ammonia. 



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

 power on polarized light of 213.5; in presence of excess of alkali this be- 

 comes 552.0, both measured for yellow light. 4 



It seems, according to the observations of many, that chondrin can, by heating 

 with hydrochloric acid, be converted into a body whose reactions resemble those of 

 syntonin, and another substance, which like the similar product from mucin, so far 

 resembles grape-sugar that it reduces cupric salts in alkaline solution ; 5 it appears, 

 however, to contain nitrogen. The existence of chondrin as a distinct substance 

 has, however, been denied 6 on the supposition that it is in all cases a mere mixture 

 of other bodies. It is stated that a substance having all the reactions of the so- 

 called chondrin, may at any time be produced by a mixture of mucin, glutin, and 

 inorganic salts. The extreme similarity in the reactions of chondrin and mucin 

 point to a close relationship between the two. The whole subject, however, requires 

 more complete investigation. With alkalies or dilute sulphuric acid chondrin gives 

 leucin, but no tyrosin or glycin. Whether chondrin exists as such in cartilage is 

 uncertain ; it seems probable that it does not, since its extraction from cartilage re- 

 quires an amount of boiling with water much greater than that requisite to dissolve 

 dried chondrin. 



Preparation. From cartilage by extracting with water and precipitating with 

 acetic acid. 



[Chondrin is not probably a distinct substance, but a mixture of mucin and 

 gelatin. ] 



Gelatin or Glutin. 7 (0, 23.21. H, 7.15. N, 18.32. C, 50.76. S, 0.56 

 per cent, ) 



This is the substance which is yielded when connective- tissue fibres are heated 

 for several days with very dilute acetic acid, at a temperature of about 15 C., or 

 by the prolonged action of water in a Papin's digester. The elastic elements of 

 connective tissue are unaffected by the above treatment. 



As obtained in this way glutin is when heated a thin fluid, solidifying on cooling 

 to the well-known gelatinous form. When dried it is a colorless, transparent, brittle 

 body, swelling up, but remaining undissolved in cold water ; heating, or the addition 

 of traces of acids or alkalies, readily effects its solution. When dissolved in water 

 it possesses a Isevo-rotatory power of 130, at 30 C. ; the addition of strong alkali 

 or acetic acid reduces this to 112 or 114, both measured for yellow light. 8 Its 

 solutions will not dialyse. 



Mercuric chloride and tannic acid are the only two reagents which yield insoluble 



1 Eichwald, op. cit. and Chem. Centralb., 1866, No. 14. Staedeler, Ann. d. Chem. u. Pharm., Bd. 

 cxi. S. 14. Landwehr, Zeitschr. f. physiol. Chem., Bd. v. (1881), S. 371. 



2 Landwehr, Zeitschr. f. physiol. Chem., Bd. vi. (1882), S. 75. 

 3 1. v. Mering, Beitrag zur Chemie des Knorpels, 1873. 



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

 6 De Bary, Hoppe-Seyler's Untersuch., Hft. 1, S. 71. 



6 Morochowetz, Yerh'and. Naturhist.-med. Ver., Heidelberg, Bd. i. (1876), Hft. 5. 



7 Not to be confounded with the vegetable proteid "gluten." 



8 Hoppe-Seyler, Hdb. d. phys. path. chem. Anal., 4 Aufl. 1875, S. 222. 



56 



