356 RETROGRESSIVE PROCESSES 



properties will be considered more fully in the section on " Ovar- 

 ian Tumors " ( Chap. xvii). The clear, glassy, yellowish sub- 

 stance contained in small cavities of ovarian tumors, which is 

 usually called "colloid/' consists of nearly pure pseudomucin. 

 All these substances yield a reducing substance on boiling with 

 acids, which is a nitrogen-containing body, glucosamin. 1 



Simple proteids (e. g., serum-globulin, serum-albumin, 

 nucleo-albumin, etc.) may, when in solution in closed cavities, 

 become concentrated through absorption of water until they 

 produce the physical appearance of " colloid." Probably the 

 colloid contents of dilated renal tubules, cavities in various 

 mesoblastic tumors, etc., are produced in this way. 



MUCOID DEGENERATION 



Mucin, in its typical form, is a compound proteid, consisting 

 of a proteid radicle and a nitrogen-containing carbohydrate, 

 glucosamin. Hence, when boiled with acids, mucin yields a 

 substance reducing Fehling's solution. Mucin is acid in reac- 

 tion, probably because of the presence of chondroitin-sulphuric 

 acid (at least in some varieties of mucin), and, therefore, is 

 characterized microchemically by staining with basic dyes. It 

 is readily dissolved in very weak alkaline solutions, is pre- 

 cipitated by acetic acid, and its physical properties when in 

 solution are quite characteristic. The term mucin, however, 

 probably covers a number of related but distinct bodies. Some, 

 such as the pseudomucins, are readily distinguished by not being 

 precipitated by acetic acid, and by being alkaline in reaction ; 

 others yield reducing substances without previous decomposition 

 with acids (paramucin) ; while even among the " true " mucins 

 certain differences in solubility exist. 2 



In the mammalian body we find mucin occurring in two 

 chief localities : (1) as a product of secretion of epithelial cells ; 

 (2) in the interstices of connective tissue, especially of tendons. 

 (The resemblance of synovia} fluid to mucin is more physical 

 than chemical.) There is also evidence that mucin or a related 

 body constitutes the cement substance between all the body- 

 cells. Corresponding to these two chief sources of mucin we 

 find mucoid degeneration occurring as distinct processes in 

 mucous membranes (or tissues derived therefrom) and in con- 

 nective tissue. 



1 Zangerle, Munch, med. Woch., 1900 (47), 414. 



2 For special consideration see Cutter and Gies, Amer. Jour. Physiol., 1901 

 (6), 155. 



