204 Rctrogrcsskr Processes. 



Mucoid degeneration of tissues should be considered as a de- 

 structive change; but the increased secretion of mucus may have 

 a favorable influence in pathological conditions, by the envelopment 

 of harmful corpuscular agencies and thus preventing inflammatory 

 irritation (dust particles, bacteria from the bronchial tubes. lar\nx, 

 pharynx and nose). 



Colloid Degeneration. 



Under the term colloid substances are included a number of 

 products of a gelatinous, brownish and tenacious character, remind- 

 ing one of half-set carpenter's glue, which, like mucus, originate 

 from the cells in "droplets, appear under the microscope as hyaline 

 balls and clumps and are entirely insoluble in alcohol, ether and 

 both hot and cold water. The substance dift'ers from mucus, how- 

 ever, in being completely soluble in acetic acid after a preliminary 

 swelling. This substance is normally found in the thyroid and 

 prostatic glands. Hypersecretion of the material leads to the forma- 

 tion of cysts (goitre of the thyroid gland, adrenal cysts in the 

 horse), which occasionally attain considerable dimensions (size of 

 a fist). [The cause of the process is unknown, but there is reason 

 to suspect that the product is the result of a change which follows 

 the fusion of the blood coloring matter with some of the mucin.. 

 It involves epithelial structures, commonly the thyroid, but is not 

 infrequently met in the kidneys, adrenals, ovaries, the cerebral hy- 

 pophysis and elsewhere in the body. The colloid material is com- 

 monly found collected in spaces lined with epithelium (or spaces 

 which probably were originally so lined), as cysts which range from 

 a minute size to that of a walnut or rarely even that of a fist. The 

 substance is an albuminate of uncertain and probably variable com- 

 position. Its stift" gelatinous consistency, brownish-yellow color 

 and transparency, together with the other features above mentioned, 

 grossly differentiate it from mucus and the hyaline substance. 

 Alicroscopically the material is of a transparent, structureless ap- 

 pearance with yellowish tint, and typically takes the acid stains. 

 When W'ithin the cells and before merging with the general colloid 

 mass, the substance is colorless and appears in globules and small 

 clumps, which, however, eventually fuse homogeneously with the 

 mass of colloid in the acinus or cell-lined space. The cells thus 

 affected are apparently not altered primarily and are affected mainly 

 by the pressure of the collection of the colloid matter, which causes 

 more or less atrophy.] 



