Mucoid Degeneration. 203 



biirsce, synovial membranes and in notable quantities in foetal con- 

 nective tissues, is often produced in excessive amounts in pathologi- 

 cal conditions and found in such quantities in the matrix of tissues 

 that it becomes evidence of a degenerative process. Increased se- 

 cretion of mucus from cells occurs for the most part as one of 

 the phenomena of inflammatory irritation, the mucus appearing as 

 an accumulation of a ropy fluid, resembling the albumen of an 

 egg (mucous catarrh ), sometimes more or less clouded from the 

 admixture of desquamated and exuded cells, hi connective tissue. 

 cartilage and bone, the occurrence of mucus causes a gelatinous 

 swelling, an appearance suggestive of head cheese. 



Under the microscope mucus may be recognized as transparent 

 droplets coalescing into clumps (mucous spheroids), usually having 

 fairlv definite outlines. The cells in which the mucus is formed 

 generally swell up in one part, the mucin causing some nuclear 

 deformation from pressure, flattening it and pushing it toward 

 the base of the cell (transformation of cylindrical cells into goblet 

 cells) ; the mucus seems to originate from the nucleus in the form of 

 a chromatic substance thrown ofl:' in small globules (hyalosomes), 

 which take a uniform blue color with hsematoxxiin and respond 

 to the xanthroproteic test (yellow coloration with nitric acid). 



[Mucoid connective tissues, under the microscope, are typified 

 by the gelatinous structure of the umbilical cord, and present a 

 delicate network of stellate cells, with mucin existing within the 

 reticular spaces as a transparent structureless intercellular sub- 

 stance.] 



Physically, mucin is characterized by swelling in water and the diffi- 

 culty of passing it through a filter; chemically it is precipitated in white 

 flocculi by the addition of acetic acid (mucoid softening), but is not 

 precipitated by ferric chloride, mercuric chloride and nitrate of silver. It 

 is insoluble in alcohol and ether. There are apparently a number of 

 forms of mucin ( Birch-Hirschfeld), among them some which are not 

 thrown down by acetic acid (pseudo-mucin, metalbumin). [Three types 

 are commonly recognized, mucin, pseudo-mucin and paramucin. The first 

 and second are usually found as products of epithelial cells; the third 

 is more apt to be met in mucoid degeneration of connective tissue. I\Iucni 

 and pseudo-mucin when heated with a mineral acid give origin to a 

 substance capable of reducing Fehling's solution; paramucin will reduce 

 it directly. They all, as ?. rule, take a blue stain with hematoxylin, but 

 vary in their staining properties with aniline dyes. It should be noted 

 here that the mucoid cells, really "goblet epithelium." of certain cancers 

 were formerly regarded as colloid, and at present are often thus spoken of; 

 but it should be definitely understood that these so-called colloid cancers 

 are improperly named, and should be denominated mucoid cancers.] 



