58 THE ALBUMINS. 



common solvents of the albumins (water and dilute saline solutions, 

 and for the most part also in dilute acids and alkalies). Their 

 solution involves their destruction. 



The elementary composition of some of the more important mem- 

 bers of the group follows : 



Gelatin (of the shops) . C = 49.38 H = 6.8 N = 17.97 S = 0.7 O = 25.13 



Glutin (tendon) . . . C = 50.11 H = 6.5 N = 17.81 S = 0.25 O = 25.24 

 Elastin (ligamentum 



nuchjfi) C = 54.08 H =: 7.2 N = 16.85 S = 0.3 



Fibroin (silk) . . . . C = 48.60 H = 6.4 N = 18.89 



Amyloid C == 53.58 H = 7.0 N = 15.04 S = 1.3 



Of special interest among the albuminoids is collagen and its 

 hydrate ylutin or gelatin. Solutions of collagen gelatinize on cool- 

 ing and redissolve on the application of heat. The mineral acids, 

 potassium ferrocyanide and acetic acid, and most mineral salts do 

 not precipitate the substance from its solutions. Pure solutions of 

 gelatin give the biuret reaction and the xanthoproteic reaction, 

 while those of Millon and Adamkiewicz are negative. An aro- 

 matic complex, however, is present nevertheless, for on hydrolysis 

 with mineral acids phenyl-alanin may be obtained, though only in 

 small amount (0.4 per cent.). Noteworthy is the large amount of 

 glycocoll (16.5 per cent.). Sulphur is present, but cannot be split 

 off as hydrogen sulphide by boiling with caustic alkali. 



On tryptic digestion collagen yields traces of leucin, but no other 

 amido-acids. Solutions of cartilaginous glutin (formerly termed 

 chondrin) possess characteristics which are different from those of the 

 glutin which is obtained from connective tissue or decalcified bone. 

 These differences are not referable to the glutin as such, but to the 

 presence of certain soluble compounds of chondroitin-sulphuricacid. 



The amyloid substance, finally, occupies a unique position among' 

 the albuminoids. It is met with only under pathologic conditions, 

 and may then be found in the parenchyma of the liver, the spleen, 

 the kidneys, etc. Like the true albumins, it consists of carbon, hy- 

 drogen, nitrogen, oxygen, and sulphur, and on decomposition yields 

 both leucin and tyrosin. It gives Millon's reaction, that of Adam- 

 kiewiez, and the xanthoproteic reaction. It is insoluble in water, 

 alcohol, ether, dilute hydrochloric acid, and acetic acid. Concen- 

 trated hydrochloric acid and solutions of the alkaline hydrates cause 

 its solution, but at the same time transform it into acid albumin or 

 alkaline albuminate. The gastric juice, contrary to what has been 

 claimed, likewise causes the substance to dissolve. Most character- 

 istic is its behavior toward iodine and aniline green. The latter is 

 colored red. Dilute aqueous solutions of iodine color the substance 

 a brownish red or a bluish violet, which passes into blue on treating 

 with sulphuric acid. lodomethyl-anilin stains the substance red, 

 especially after previous treatment with acetic acid. 



