RKTROCKKSSIVK TlSSrii (_' 1 1 A .NGKS. 215 



Pathologic. 



Pathologic mucoid formation affects cells and intercellular 

 substance. Celhilar ])athoh)gic mucoid change is identical to 

 normal mucus formation except that it is in abnormal locations 

 or is in excess in those locations in which mucus is normally 

 produced. Intercellular mucoid formation is a condition result- 

 ing from the conversion of intercellular suljstances — fibres, 

 matrix of cartilage and bone — into mucus. Pathologic mucoid 

 changes occur rather freciuentl}'. It is evident in catarrhal in- 

 flammation, in cyst formations and as a retrogressive process in 

 many tumors. 



Etiology. — The cause of pathologic nuicoid changes is not 

 known. Excessive cellular mucoid formation accompanies mild 

 inflammatory disturbances of mucous membranes — so called 

 catarrh. The increased production of mucus in catarrhal inflam- 

 mation may be the expression resulting from the exaggerated 

 function of the mucous membrane induced by the excessive 

 quantity of blood supplied. 



Intercellular mucus formation may result from improper 

 nutrition or injurious influences induced by chemic substances. 

 It has long been thought, although it has never been proven, 

 that some product is evolved when the thyroid gland is dis- 

 eased that causes a mucus degeneration of all fibrous tissue in 

 the body ( my.xoedema) . Some sarcomata and carcinomata are 

 affected with mucoid changes, probably the result of chemic sub- 

 stances elaborated hx the tumor cells. 



Appearance. — Macroscopic. — ^Mucus of pathologic origin is not 

 dift'erentiable from physiologic mucus. In pathologic conditions 

 accompanied bv mucus formation the mucus is frequently mixed 

 with other substances, as blood, pus and food stuff. Thus the 

 mixture assumes various appearances. A discharge composed 

 of mucus and pus (muco-purulent) is common in practically all 

 catarrhal inflammation, being the characteristic discharge of 

 catarrhal pneumonia and is the usual discharge from the respira- 

 tory tract and conjunctiva, in dogs affected with distemper, in 

 horses afflicted with "stock yard fever," etc. 



The appearance of a tissue affected with pathologic mucus 

 changes, regardless of whether the cells or intercellular sub- 

 stance is involved, depends upon the quantity of mucus pro- 

 duced. If there is a limited quantity of mucus and it is equally 

 distributed throughout, the aft'ected tissue will appear swollen 

 and soft. If more extensive and diff'use the affected tissue will 

 be soft, spongy, and slimy. If the entire structure has practically 

 been converted into a mass of mucus, it will appear as a slimy, 



