ALBUMINS OR PROTEINS. 143 



some extent dissolved, and to some extent they participate in the con- 

 struction of tissue. Their classification is based upon principles morpho- 

 logical rather than chemical-physical. They are sometimes included with 

 the mucins, and sometimes classed as an independent group. We shall 

 mention only the most important of them. Deserving of mention are the 

 mucoids prepared from tendons, bones, and cartilages. The last named 

 has been thoroughly investigated. Chondro-mucoid in conjunction with 

 collagen constitutes the elementary material of cartilage. It contains 

 considerable sulphur and a reducing sugar. When hydrolyzed we obtain 

 a protein and a carbohydrate-ethereal sulphuric acid, the so-called chon- 

 droitin-sulphuric acid. 1 This is a colloidal substance, and has been investi- 

 gated by Schmiedeberg, 2 and later by A. Orgler and C. Newberg. 3 By 

 boiling with acids for a short time it decomposes into sulphuric acid and 

 a residue, chondroitin, free from sulphuric acid. Further treatment with 

 acid produces an amido-polysaccharide, whose exact nature has not yet 

 been determined. Chondroitin-sulphuric acid is found not only in carti- 

 lages, but also in bones in ligamentum nuchce, and in the mucous mem- 

 brane of the pig. It occurs especially in amyloid, a protein which is 

 found in the tissues under certain pathological conditions. Morner 4 

 found chondroitin-sulphuric acid repeatedly in the urine to the extent of 

 0.05 per cent. 



The proteins found in the vitreous humor, in the cornea, and in the um- 

 bilical cord, also belong to the group of mucoids, as does the ovomucoid 

 obtained from the white of an egg. The latter may be isolated by coagu- 

 lating the globulin and albumin, and adding alcohol to the filtrate. A 

 reducing substance, gluocsamine, can be split off from it. Steudel 5 ob- 

 tained 29.4 grams glucosamine from 100 grams ovomucoid. Blood serum 

 also contains a mucoid body. Morner describes another substance be- 

 longing to this group, which he obtained from the urine. An analogous 

 product also occurs in the ascitic fluid. 



We must admit that a large amount of uncertainty attaches to this 

 group of albuminous substances. Secure foundations are lacking. It is 

 practically impossible to purify these products, beyond getting rid of 

 gross impurities. The properties of the various members of this group 

 are such, that it is very difficult to work with them. It is difficult to ob- 

 tain them in large quantities. We must, therefore, look with skepti- 

 cism upon all new mucins and mucoids, and should await the time when 

 purely chemical investigations will have sufficiently classified the mem- 



C. T. Morner: Skand. Arch. f. Physiol. 1, 210 (1889). Cf. Lecture III, p. 49. 

 O. Schmiedeberg: Arch. exp. Path. Pharm. 28, 355 (1891). 

 A. Orgler and C. Neuberg: Z. physiol. Chem. 37, 399 (1903). 

 K. A. H. Morner: Skand. Arch. Physiol. 6, 332 (1895). 

 H. Steudel: Z. physiol. Chem. 34, 353 (1901-02). 



