APPENDIX. 741 



may be prepared from ox-gall, by acidulation with acetic acid and sub- 

 sequent filtration, or from ox-gall by precipitation with alcohol, after- 

 wards dissolving in water, and again precipitating by means of acetic 

 acid. It can also be obtained from mucus by diluting it with water, fil- 

 tering, treating the insoluble portion with weak caustic alkali, and pre- 

 cipitating the mucus with acetic acid. 



Properties. Mucin has a ropy consistency. It is precipitated by al- 

 cohol and by mineral acids, but dissolved by excess of the latter. It is 

 dissolved by alkalies and in lime water. It gives the proteid reaction 

 with Millon's reagent and nitric acid, but not with copper sulphate. 

 Neither mercuric chloride nor tannic acid gives a precipitate with it (?). 

 It does not dialyze. 



(c) Elastin is found in elastic tissue, in theligamenta subflava, liga- 

 mentum nuchae, etc. 



Take the fresh ligamentum nuchae of an ox, cut in pieces, and boil 

 in alcohol and ether to remove the fat. Kemove the gelatin by boiling 

 for some hours in water. Boil the residue with acetic acid for some 

 time, and remove the acid by boiling in water, then boil with caustic 

 soda until it begins to swell. Kemove the alkali, and leave it in cold 

 hydrochloric acid for twentj^-four hours, and afterwards wash with 

 water. 



Properties. It is insoluble, but swells up both in cold and hot water. 

 Is soluble in strong caustic soda. It is precipitated by tannic acid; does 

 not gelatinize. Gives the proteid reactions with strong nitric acid and 

 ammonia, and imperfectly with Millon's reagent. Yields leucin on boil- 

 ing with strong sulphuric acid. 



(D) Chondrin is found in cartilage. 



It is prepared by boiling small pieces of cartilage for several hours, 

 and filtering. The opalescent filtrate will form a jelly on cooling. 

 Chondrin is precipitated from the warm filtrate on addition of acetic 

 acid. 



Properties. It is soluble in hot water, and in solutions of neutral 

 salts, e.g., sulphate of sodium, in dilute mineral acids, caustic potash, 

 and soda. Insoluble in cold water, alcohol, and ether. It is precipitated 

 from its solutions by dilute mineral acids (excess redissolves it), by alum, 

 by lead acetate, by silver nitrate, and by chlorine water. On boiling with 

 strong hydrochloric acid, it yields grape-sugar, and certain nitrogenous 

 substances. Prolonged boiling in dilute acids, or in water, destroys its 

 power of forming a jelly on cooling. 



(E) Keratin is obtained from hair, nails, and dried skin. It con- 

 tains sulphur evidently only loosely combined. 



(3.) Decomposition Nitrogenous products. These are formed by the 

 chemical actions which go on in digestion, secretion, and nutrition. 



