426 ji'ETh'odh'iussn j: vii amies 



name "colloid"' is given. Looking at the matter in this waj^ we must 

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

 bodies : 



Thyroid colloid, the physiological prototype of the group. This 

 consists of a compound of globulin with an iodin-eontaining substance, 

 thyroiodin, the compound protein being called bj^ Oswald iodothyreo- 

 globulin. It occurs pathologically only in cystic and similar chauges 

 in the thyroid or accessory thyroids. Being a specific product of the 

 thyroid (and perhaps of the hypophysis) 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 thy- 

 roid colloid is discussed more fully under "Diseases of the Thyroid," 

 Chap. XX.) 



Mucin, when secreted in closed cavities, as in tumore, where it be- 

 comes thickened by partial absorption of the water, may take on a 

 "colloid" appearance while retaining its chemical and tinctorial char- 

 acteristics. 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 chemical 

 luiture and its origin from specialized epithelial cells, and the process 

 should properly be considered as a "mucoid degeneration." 



Pseudomucin, which difi'ers from mucin in not being precipitated 

 by acetic acid, is a common component of ovarian cysts, and when 

 somewhat concentrated by absorption of water, forms a "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. xvii). The clear, 

 glassy, yellowish substance contained in small cavities of ovarian tu- 

 mors, 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, f/Jucosamin^^ 



Simple proteins {e. g., serum-globulin, serum-albumin, nucleo- 

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

 centrated through absoi*ption 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 pro- 

 duced in this way. 



isVirchow's Arcli., 1000 (IS;")), 410: von Simior, ibid., lOl.j (210), 2711. 

 10 Ziinpcrle. Miindi. mod. Wodi., 10(10 (47). 414. 



