444 CHEMISTRY OF THE TISSUES. 



f 2. Add acetic acid. A precipitate will fall. Let it settle. 

 Pour off the liquid and pour on glacial acetic acid. Generally 

 it will not dissolve. 



f 3. Add acetic acid with solution of potassium ferrocyanide. 

 If the miicin is pure no turbidity will appear at first, but will 

 do so after the solution has stood for some time. 



4. Add mercuric chloride. No precipitate. 



5. Add basic lead acetate. A copious precipitate will form. 

 f Reaction with Cupric Oxide, Add liquor potassre and a 



little cupric sulphate to a solution of mucin. The cupric hy- 

 drate will be dissolved. ]>oil. The liquid will still remain of 

 a clear blue color. This distinguishes mucin from albumin, 

 pepsine, and gelatin, which give a violet or red color. 



** 46. Ordinary Connective Tissue. Tendons. 



Gelatigenous Substance, or Collagen. This substance 



forms the organic basis of bones and teeth, and the principal 



or fibrous part of connective tissue, tendons, ligaments, and 



tae. 



J'ri-fnirdfit.ni. (a) From HIHH-H. Soak some bones in hydro- 

 chloric acid diluted with 8 or 9 times its bulk of water, chang- 

 ing the acid several times. This will remove the inorganic 

 salts which arc deposited in the bone and impart hardness to 

 it; so that when they are entirely removed, the bone will retain 

 its original shape, but be quite soft and pliable. The time 

 during which the bones must be soaked in order to remove the 

 whole of the salts they contain, varies with their size ; but if 

 the bones be cut into small pieces, or thin bones such as ribs 

 are used, a day or two is sufficient. Wash them well with 

 water to remove the acid and dry them over the water bath. 



(b) Frnm Tcmln).*.. After removing the mucin from tendons 

 by means of lime or baryta water (.see 45), wash the swollen 

 pieces first with water, and then with a little acetic acid much 

 diluted, so that they contract and do not again swell. Then 

 soak and wash them for a while in water, changing it several 

 times. 



Characters. When fresh, it is soft, but it shrinks and be- 

 comes hard when it is dried or alcohol is added to it. 



,SW //A //////. 1. In cold water, it will not dissolve. 2. Boil 

 the water. It will dissolve and be convened into gelatin. 

 On cooling, it will form a jelly. 3. In cold dilute acetic or 

 other acid, it will swell up. 4. In boiling dilute acids, it is 

 dissolved and converted into gelatin still more readily than 

 by water. 5. In hot liquor potassrc, it dissolves tolerably 

 easily. 



47. Gelatin. /'reparation. Boil collagen obtained from 

 bones or sinews in the manner already described. Filter the 

 solution hot. Divide the filtrate into three parts. Allow one 

 of them to cool; it will form a jelly. Evaporate another to 



