HYALOGENS. 171 



salts; it is also precipitated by several metallic salts. If mucin is heated 

 on the water-bath with dilute hydrochloric acid of about 2 per cent, 

 the liquid gradually becomes a yellowish or dark brown, and reduces 

 copper salts in alkaline solutions. 



The mucin most readily obtained in large quantities is the submax- 

 illary mucin, which may be prepared in the following way: The filtered 

 watery extract of the gland, free from form-elements and as colorless 

 as possible, is treated with 25 per cent hydrochloric acid, so that the 

 liquid contains 1.5 p. m. HC1. On the addition of the acid the mucin 

 is immediately precipitated, but dissolves on stirring. If this acid liquid 

 is immediately diluted with 2-3 vols. of water, the mucin separates and 

 may be purified by redissolving in 1-5 p. m. acid, and diluting with 

 water and washing therewith. The mucin of the navel-cord may be 

 prepared in the same way. As a rule the mucins can be prepared by 

 precipitation with acetic acid and repeated solution in dilute lime-water 

 or alkali, and reprecipitation with acetic acid. Finally they are treated 

 with alcohol and ether. In the preparation of sputum mucin the method 

 is very complicated (Fit. MULLER). 



Mucoids or Mucinoids. In this group we must include those non- 

 phosphorized glycoproteins which are neither true mucins nor chondro- 

 proteids, although they show among themselves such differences in 

 behavior that they can be divided into several subgroups of mucoids. 

 To the mucoids belong pseudomutin, the probably related body colloid, 

 ovomucoid, and other bodies, which on account of their differences will be 

 best treated individually in their respective chapters. 



Hyalogens. Under this name KRUKENBERG l has designated a number of 

 different bodies, which are characterized by the following: By the action of 

 alkalies they change, with the splitting off of sulphur and some nitrogen, into 

 soluble nitrogenized products called by him hyalines, and which yield a pure car- 

 bohydrate by further decomposition. We find that very heterogeneous sub- 

 stances are included in this group. Certain of these hyalogens seem undoubtedly 

 to be glycoproteins. Neossin 2 of the Chinese edible swallow's-nest, membranin 3 

 of DESCEMET'S membrane and of the capsule of the crystalline lens, and spiro- 

 graphin 4 of the skeletal tissue of the worm Spirographis, seem to act as such. 

 Others, on the contrary, such as hyalin 5 of the walls of hydatid cysts, and onu- 

 phin* from the tubes of Onuphis tubicola, do not seem to be compound proteins. 

 The so-called mucin of the holothuria, 7 and chondrosin 8 of the sponge, Chondrosia 



1 Verb. d. physik.-med. Gesellsch. zu Wiirzburg, 1883; also Zeitschr. f. Biologie, 22. 



2 Krukenberg, Zeitschr. f . Biologie, 22. 



3 C. Th. Morner, Zeitschr. f. physiol. Chem., 18. 



4 Krukenberg, Wiirzburg, Verhandl., 1883; also Zeitschr. f. Biologie, 22. 



6 A. Liicke, Virchow's Arch., 19; also Krukenberg, Vergleichende physiol. Stud., 

 Series 1 and 2, 1881. 



6 Sch'miedeberg, Mitth. aus d. zool. Stat. zu Neapel, 3, 1882. 



7 Hilger, Pfliiger's Archiv, 3. 



8 Krukenberg, Zeitschr. f . Biologie, 22. 



