404 THE SUPPORTING TISSUES. 



soluble in water. A concentrated solution resembles mucilage in 

 appearance and consistence. Its salts are also for the most part 

 soluble in water. The sodium and potassium salts can be pre- 

 cipitated by means of ferric chloride, lead subacetate, and alcohol, 

 while silver nitrate, zinc chloride, tannic acid, and potassium ferro- 

 cyanide, the latter in the presence of acetic acid, are without effect. 



In the cartilage its potassium and sodium salts occur both as such 

 and in combination with collagen and albumins. A mixture of these 

 compounds, according to Schmiedeberg, constitutes the so-called 

 chondromucoid of Morner. If a solution of gelatin is mixed with 

 an acidified solution of the potassium or sodium salts of the acid, 

 a precipitate occurs. This also results if cartilage is boiled with 

 water and the resulting impure solution of gelatin, which was 

 formerly termed chondrin, is acidified with a dilute mineral acid. 

 The precipitate consists of the free chondroitin-sulphuric acid, and 

 is soluble in an excess of the acid. 



Chondroitin-sulphuric acid, while essentially a constituent of 

 hyaline cartilage, has also been found in elastic and fibrous carti- 

 lage, in bone, in the inner coats of the larger arteries, in the chon- 

 dromas, in the amyloid substance obtained from liver, in the 

 mucosa of the pig's stomach, and in the ligamentum nuchse. Traces 

 are likewise found in the urine. 



Isolation. To isolate chondroitin-sulphuric acid from cartilage 

 shavings, the material is boiled with a 5 per cent, solution of caustic 

 alkali. The solution is neutralized, and freed by filtration from 

 the alkaline albuminates which have been formed during the process 

 of boiling. Albumoses are removed by means of tannic acid, the 

 excess of the latter by means of lead subacetate, and the excess 

 of lead with hydrogen sulphide. The acid is then precipitated with 

 alcohol. To purify the substance, it is dissolved in water, and the 

 solution dialyzed and reprecipitated with alcohol. The solution in 

 water and precipitation with alcohol is repeated several times, when 

 the acid is finally washed with alcoholic ether. 



Isolation of Chondromucoid. To isolate the chondromucoid, 

 viz., the compounds of chondroitin-sulphuric acid with collagen 

 and albumins, the cartilage shavings are first extracted with water, 

 which dissolves the free chondroitin-sulphuric acid and a small 

 amount of the chondromucoid. On acidulating this solution with 

 a 3 pro mille solution of hydrochloric acid and heating on a water- 

 bath, the chondromucoid is gradually precipitated, while the free 

 acid remains in solution. The cartilaginous residue is then ex- 

 tracted with a 2 to 3 pro mille solution of hydrochloric acid at a 

 temperature of 35 to 40 C., which dissolves any collagen that 

 may be present as such. After washing with water the remaining 

 material is extracted with a 5 pro mille solution of caustic alkali. 

 The chondromucoid is thus dissolved, and is then precipitated with 

 an acid. After repeated solution in an alkali and precipitation 

 with an acid it is finally washed with alcohol and ether. 



