COLLOID DEGENERATION. 39 



about includino; mucous softenino; amono- the varieties of retro- 

 grade metamorphosis. The characteristic fact remains, that 

 mucous softening of the connocti\e tissues may take place on the 

 one hand, without any important alteration in the form and 

 arrangement of the cells (mucous tissue), and on the other hand, 

 in connexion with the most various progressive and retrograde 

 changes in them. 



D. Colloid Degeneration. 



§ 44. We come now to the last member of the series of 

 " Conditions of Involution " to which the tissues are liable. 

 Colloid degeneration is closely related to mucous softening. 

 Their respective appearances, both naked-eye and microscopic, are 

 in some specimens so much alike, that a long period elapsed before 

 men learned to distinguish between a connective tissue whose 

 matrix had undergone mucous softening and one whose cells had 

 undergone colloid degeneration. The superficial resemblance 

 between the two, gave rise to the greatest confusion in the 

 nomenclature of tumours ; the terms colloid, collonema, sar- 

 coma gelatinosum, hyalinum, carcinoma colloides, being indis- 

 criminately applied to one or other variety. What is the basis 

 of this similarity ? We find in either case a transparent, swollen, 

 tremulous jelly, traversed by a network of fibres. Now, the 

 mere discovery that in the one case the network was made up 

 of stellate anastomosing cells, while in the other it consisted of 

 the residue of a fibrillated matrix, sufficed to compel the separa- 

 tion of colloid from mucous tissue, a separation wliich was 

 justified by further researches. In the first place, colloid dege- 

 neration is characterised by the presence of a chemical compound, 

 differing from mucin by its neutral attitude towards those re- 

 agents which act upon mucus, e.g. acetic acid, as also by its 

 elementary composition, which places it among those albuminates 

 which contain sulphur. 



Not less important for the independence of colloid degenera- 

 tion is the fact that, in its first stage at least, it is always a 

 metamorphosis of cells. 



This brings us at once to the essential feature of its 



o 



anatomy. The only form in which colloid matter presents 

 itself to the microscopist is that of a colourless, transparent 

 globule, with an oily lustre, the so-called " colloid sphere. " How 



