132 CARTILAGE. BONE. 



CARTILAGE. 



293. This contains collagen mixed with chondrogen, 

 chondroitin sulphuric acid and an albuminoid. It can be 

 obtained from pigs' tracheas. Separate the surrounding 

 tissues,, grind the remainder and boil with water. The fil- 

 tered solution yields a jelly when it cools (gelatin from 

 the hydration of the collagen) . 



294. The solution gives no reaction for sulphuric 

 acid with barium chlorid but does so after boiling for some 

 time with hydrochloric acid, showing that it contains an 

 organic sulphate (page 173)., chondroid, in sulphuric acid. 



295. The solution reduces Trommer's or Fehl ing's 

 reagent after boiling, but not before. It gives the protein 

 reactions. 



BONE. 



Bone contains an organic compound, collagen, and a 

 number of inorganic or mineral substances. These latter 

 are the phosphates of calcium and magnesium, mainly the 

 former; also calcium carbonate and small amounts of cal- 

 cium chlorid and fluorid. The inorganic substances can 

 be removed by acids, leaving the bone flexible. If a bone 

 is heated the collagen is decomposed, with an evolution of 

 ammonia, showing that the collagen is a nitrogenous com- 

 pound. Then inflammable gases are set free. If the igni- 

 tion is performed where free access of air is prevented, 

 there remains a black mass known as bone-black or animal 

 charcoal. The black color is due to carbon, which can be 

 removed by burning in the air, leaving the mineral or in- 

 organic constituents only. The bone-black is an extremely 

 porous substance and has the power of absorbing from 

 their solutions many of the vegetable coloring matters and 



