354 RETROGRESSIVE PROCESSES 



nephritis, thickened pleural, pericardial, and episplenitis scars, 

 etc. Such hyaline substance occurs independent of the usual 

 causes of amyloid, affects only abnormal fibrous tissue, never 

 changes into amyloid, and is prone to undergo calcification it 

 surely has no close chemical relation to the form of hyalin that 

 does become amyloid. Presumably, it is similar in nature 

 to the collagen of normal fibrous tissue intercellular substance, 

 which has undergone physical rather than chemical changes into 

 a homogeneous hyaline substance. For its physiological proto- 

 type it has the thick " collagenous " fibers of the subcutaneous 

 connective tissue. 



Probably of quite different origin is the hyalin that develops 

 from elastic tissue, as seen best in the thick-walled, partly oblit- 

 erated arteries of the senile spleen ; and less characteristically in 

 the early stages of arteriosclerosis, since here the preceding form 

 of connective-tissue hyalin may also occur. Although arterial 

 elastic tissue is related chemically to amyloid, these hyaline ves- 

 sels do not develop the usual amyloid reaction, but remain more 

 or less of the specific, elastic tissue stains. Presumably this 

 form of hyalin is an increased and physically altered elastin. 1 



Epithelial hyalin occurs within the cells, and includes 

 substances of presumably widely diverse chemical nature, from 

 the keratin of squamous epithelium to the small intracellular 

 hyaline granules of carcinoma and other degenerating cells (Rus- 

 sell's fuchsin bodies 2 ). Extracellular substances of hyaline 

 character, but of unknown composition, may also be produced 

 by epithelium ; e. g., hyaline casts in the renal tubules. 



Many other pathological materials of widely differing nature 

 may, under certain conditions, assume a hyaline appearance ; 

 e. g.j fibrinous exudates and thrombi, degenerated muscle-fibers 

 (Zenker's or " waxy " degeneration), tumor-cells (cylindroma), 

 etc. In all of these the chemical nature of the parent substance 

 or substances is probably much less altered than its physical 

 appearance, but whether the change is related to the process of 

 proteid coagulation or not is unknown. 



COLLOID DEGENERATION 



This term, also, has a very indefinite meaning, and is applied 

 to many different conditions by various authors. Thus, v. 

 Recklinghausen includes under this name amyloid, epithelial 

 hyaline, and mucoid degeneration. Marchand includes hyaline 

 connective-tissue degeneration, and, also, as do most other 



1 See Schmidt, Verb. Deut. path. Gesell., 1904 (7), 2. 



2 Literature, see Hektoen, Progressive Med., 1899 (ii), 241. 



