34 MUCOTTS SOFTENING. 



terised tlie changes caused by age in the last mentioned structures 

 as tending to produce an imperfect articular cavity (Gelenkhohle). 



The cavity is produced by a gradual softening of the cartila- 

 ginous investment (liberzug) of the opposed surfaces of adjoining 

 vertebral centra. The anatomical appearances presented by this, 

 as by every other form of softening in cartilage, are highly 

 characteristic. The homogeneous matrix exhibits dark striae 

 at right angles to the free surface, which prove at a later period to 

 be the initial stage in the splitting up of the tissue into fibres. 

 The real fibrillation then ensues, beginning at the free surface ; 

 the individual fibres separate from one another and float loosely 

 in the articular fluid ; their free extremities soon become acumi- 

 nated and terminate in blunt points. It is here that the inter- 

 cellular substance undero;oes solution in the course of mucous 

 softening. The accompanying process in the cartilage cells ex- 

 hibits the characters of a progressive, not a retrograde change, 

 inasmuch as a proliferation of cells by fission takes place ; 

 the result beincr, that instead of sinorle cartilao^e-cells, 

 groups consisting of from two to twenty cells are formed. 

 These cell-nests, surrounded by a capsule and a residue of inter- 

 cellular substance, mingle with the fluid products of softening, 

 where they undergo colloid degeneration.* 



The process of softening in bone tissue is complicated by the 

 necessity for a previous solution and removal of the earthy salts 

 with which its matrix is impregnated, before the liquefaction of 

 the matrix itself can begin. We often find, however, that these 

 two processes, viz. decalcification and liquefaction of matrix, are 

 so nearly simultaneous, that the bone tissue at the limit of 

 absorption is bounded byaperfectlysharp line, curiously indented, | 



* I cannot assent to K6lliJ:er's ingenious theory, according to which 

 the numerous white corpuscles which may be seen, even without the aid 

 of a microscope, in the central jelly of the inter-vertebral discs, arc 

 descended from the original cells of the notochord. From the analogy 

 of morbid softening of cartilage, I regard them as being nests of cartilage 

 cells liberated b^^ softening of the matrix, and subsequently affected by 

 colloid degeneration. 



t What are known as Hoicshys lacunae (fig. 10) are due to the un- 

 equal rate at which the decalcification of the osseous tissue proceeds. 

 The direction of the stellate processes of the bone corpuscles, with refer- 

 ence to the surface from which resolution is proceeding, seems to exert 

 some sort of guiding influence in the matter. (Cf. Diseases of Bone.) 



