APP.] CHEMICAL BASIS OF THE ANIMAL BODY. 725 



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 1 ; it appears however to contain 

 nitrogen. The existence of chondrin as a distinct substance has however 

 been denied 2 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 

 alkalis 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 

 requires 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. 



Gelatin or Glutin 3 . (O, 23-21. H, 7-15. N, 18-32. C, 50-76. 

 S, -56 p. c.) 



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, solidi- 

 fying on cooling to the well-known gelatinous form. When dried it is 

 a colourless, transparent, brittle body, swelling up, but remaining undis- 

 solved in cold water; heating, or the addition of traces of acids or 

 alkalis, 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 4 . Its solutions will not dialyse. 



Mercuric chloride and tannic acid are the only two reagents which 

 yield insoluble precipitates with this body. Its presence prevents the 

 action of Trommer's sugar test, since it readily dissolves up the 

 precipitated cuprous oxide. The proteid reactions of glutin are so 

 feeble that they are probably due merely to impurities. Heated with 

 sulphuric acid it yields ammonia, leucin and glycin, but no tyrosin. 



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



2 Morochowetz, Verhand. naturhist. med. Ver. Heidelberg. Bd. I. (1876) Hft. 5. 



3 Not to be confounded with the vegetable proteid 'gluten.' 



4 Hoppe-Seyler, Hbd. d. phys. path. diem. Anal. 4 Aufl. 1875, S. 222. 



