430 RETROGRESSIVE CHANGES 



logically and macroscopically descriptive of certain products of cell 

 activity or disintegration, which have nothing in common except the 

 fact that they form a thick, glue-like or gelatinous, often yellowish or 

 brownish substance. There is 7io one definite substance colloid, accord- 

 ing to the usual usage of the word in pathological literature, but many 

 different protein substances may assume the appearance to which the 

 name "colloid" is given. Looking at the matter in this way, we must 

 recognize as the usual "colloid" substances, the following chemical 

 bodies: 



Thyroid colloid, the physiological prototype of the group. This consi.sts of 

 a compound of globulin with an iodin-containing substance, thj^roiodin, the com- 

 pound protein being called by Oswald iodothyreoglobulin. It occurs pathologi- 

 cally only in cystic and similar changes in the thyroid or accessory thyroids. Being 

 a specific product of the thyroid with definite physiological properties, it manifestly 

 has only a morphological relation to the other forms of colloid found in degenerating 

 tumors, etc. In cysts of the thyroid, and less often in tumors, there is occasionally 

 found a more dense "colloid" material of deeper color, the "caoutchouc colloid" 

 of the Germans; this seems to result largely from transformation of red corpuscles 

 in hemorrhagic cysts (Wiget).** (The nature of thyroid colloid is discussed more 

 fully under " Diseases of the Thyroid," Chap, xxii.) 



Mucin, when secreted in closed cavities, as in tumors, where it becomes thick- 

 ened by partial absorption of the water, may take on a "colloid" appearance while 

 retaining its chemical and tinctorial characteristics. This is particularly observed 

 in the "colloid" carcinomas which arise especially from the mucous membrane of 

 the alimentary tract. This substance is, of course, quite specific both in its chem- 

 ical nature and its origin from specialized epithelial cells, and the process should 

 properly be considered as a "mucoid degeneration." 



Pseudomucin, which differs from mucin in not being precipitated by acetic acid, 

 is a common component of ovarian c.ysts, and when somewhat concentrated by 

 absorption of water, forms "typical colloid." Because it is alkaline, this form of 

 colloid tends to stain rather with the acid dyes (eosin, acid fuchsin, etc.), while 

 true mucin stains with basic dyes. Several varieties of pseudomucin have been 

 described by Pfannenstiel, and their properties will be considered more fully in 

 the section on "Ovarian Tumors" (Chap. xix). The clear, glassy, yellowish sub- 

 stance contained in small cavities of ovarian tumors, which is usually called 

 "colloid," consists of nearly pure pseudo-mucin. All these substances yield a 

 reducing substance on boiling with acids, which is a nitrogen-containing body, 

 glucosmnin.^^ 



Simple proteins (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 phj^sical 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 protein, consisting of a 

 protein radical and a conjugated sulphuric acid which contains a 

 nitrogenous sugar. Hence, when boiled with acids, mucin yields a 

 substance reducing Fchling's solution. Mucin is acid in reaction, 

 probably because of the presence of the sulphuric acid and, therefore, 

 is characterized microchemically by staining with basic dyes. It is 

 readily dissolved in very weak alkahne solutions, is precipitated by 



68 Virchow's Arch.. 1906 (185), 416; von Sinner, ibid., 1915 (219), 279. 

 «9Zangerle, Munch, med. Woch., 1900 (47), 414. 



