MUCO1DS. 167 



diately 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 (Fn. MULLER). 



The precipitation by acetic acid, as shown by HAMMARSTEN,* is not applicable 

 in the preparation of submaxillary mucin, because another protein substance is 

 precipitated with the mucin, but remains in solution on using the hydrochloric- 

 acid method above described. POSNER and GIES 2 have by special experiments 

 shown the power of mucins of precipitating proteins, and this makes the ordi- 

 nary method of precipitating with acetic acid questionable. 



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 pseudomucin, 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 3 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 substances 

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

 be glycoproteins. Neossin * of the Chinese edible swallow 's-nest, membranin 5 

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

 graphin 6 of the skeletal tissue of the worm Spirographis, seem to act as such. 

 Others, on the contrary, such as hyalin 1 of the walls of hydatid cysts, and onu- 

 ptiin, 6 from the tubes of Onuphis tubicola, do not seem to be compound proteins. 

 The so-called mucin of the holothurice 9 and chondrosin 10 of the sponge, Chondrosia 

 reniformis, and others may also be classed with the hyalogens. As the various 

 bodies designated by KRUKENBERG as hyalogens are very dissimilar, it is not 

 of much advantage to arrange these in special groups. 



1 Zeitschr. f . physiol. Chem., 12. 



2 Amer. Journ. of Physiol., 11. 



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



4 Krukenberg, Zeitschr. f. Biologie, 22. 



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



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



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

 Series 1 and 2, 1881. 



8 Schmiedeberg, Mitth. aus d. zool. Stat. zu Neapel, 3, 1882. 



9 Hilger, Pfliiger's Archiv, 3. 



10 Krukenberg, Zeitschr. f. Biologie, 22. 



