THE PROTEIN SUBSTANCES. IO/ 



repeated several times give a nearly constant product. The 

 analyses show 48-49 per cent of carbon, 30 of oxygen and 

 below 12 of nitrogen. A small amount of sulphur is present. 



In cartilage, along with collagen and albuminoid bodies, a 

 very important mucoid known as chondro-mucoid is found. 

 This has a composition not very different from the tendon 

 product just given, but contains over 2 per cent of sulphur, 

 part of which is in peculiar ethereal combination. This ether- 

 eal product is separated by cleavage with dilute acids or alka- 

 lies and is known as chondroitin sulphuric acid, and, according 

 to Schmiedeberg, has the composition C 18 H 27 NO 14 .SO 3 . On 

 hydrolysis this acid yields chondroitin, C 18 H 27 NO 14 , and sul- 

 phuric acid; the chondroitin furnishes acetic acid and chon- 

 drosin, C^HgiNOu ; finally further hydrolysis breaks the 

 chondrosin down into glucoseamine and glucoronic acid, ac- 

 cording to the same author, but later researches seem to indi- 

 cate that the cleavage is not as simple as suggested. It has 

 been shown also that this complex acid is not peculiar to carti- 

 lage, but is found in many substances belonging to the albu- 

 minoid group of proteins as well. Although widely distrib- 

 uted the physiological importance of the body has not yet been 

 determined. 



In addition, mucoid substances have been recognized in 

 urine, in blood serum, in white of egg and several pathological 

 transudates in small amount. 



ALBUMOIDS OR ALBUMINOIDS. 



These substances differ from the real proteins both phys- 

 ically and chemically; the physical differences are, however, 

 the most pronounced and characteristic. The important 

 bodies grouped here contain the different kinds of gelatin or 

 glue-forming compounds, the horn substances, the spongin of 

 the sponge, elastin of the so-called elastic tissues of the body 

 and other substances of less importance. They are all firmer 

 and harder than the common proteins and as a rule quite in- 

 soluble in water, and in general resistant against the action of 



