312 SPECIAL HISTOLOGY. 



101) ; the third and greatest part, ultimately becomes ossified, and 

 constitutes all the bones of the trunk and extremities, and a great part 

 of those of the cranium. All these bones are ossified, essentially in the 



compressed, and dark. Under favorable circumstances, the cells, in simple cartilage, may 

 be isolated, and their peculiar relations with regard to acetic acid, which generally renders 

 them darker and collapsed, may be exhibited. Water also causes them to collapse, and 

 they thus occasionally form peculiar, jagged corpuscles, which one might be readily tempted 

 to confound with branched cells. The larger the original cell was, so much the more 

 branched does its collapsed mass appear." (p. 152.) "It might have been ex- 

 pected that in the course of ossification of the cartilage, these cells would be seen to pass 



into the irregular, anastomosing bone-corpuscles ; but nothing of the kind is visible 



A point of difficult determination is, in general, the existence of actual cells in the small flat 

 cavities of cartilage, e. g. towards the surface. Very frequently it would here seem as if the 

 membrane of the cell had coalesced with the intercellular substance, and only the contents 

 with the nucleus had remained behind. But on careful investigation especially under the 

 prolonged operation of acetic acid, frequently after maceration in hydrochloric acid, we 

 clearly see a complete cell with a nucleus and contents in the cavity" (p. 153). 



Virchow gives no figures, but the above passages furnish so accurate an account of what 

 we have ourselves seen in young and in fully-formed cartilage, that we have thought we 

 could not do better than cite them. The jagged appearance of the corpuscles to which he 

 refers, is very common, and we have been led to suspect that it may arise from the same 

 cause as the very similar appearance often exhibited by the colorless corpuscles of the blood, 

 viz., a protean throwing out of processes. 



When Virchow, however, describes the passage of these " cells" into the branched or 

 stellate corpuscles of fibro-cartilage, and considers the latter to be metamorphosed cartilage- 

 corpuscles, he confounds together things which are essentially different. Careful examina- 

 tion of foetal fibro-cartilage, e. g. the intervertebral fibro-cartilage of the Kitten, shows that 

 the stellate body is the wall of the cartilage cavity, with processes which run out from it, the 

 original corpuscle remaining in the interior of the cavity, either unchanged or becoming 

 gradually lost, or fused into one mass with its walls. 



The account of the structure of cartilage given by Tomes and De Morgan (1. c., pp. 15, 

 16) in all essential points agrees with that of Virchow. They call the corpuscles, granular 

 cartilage cells. 



To recapitulate : the facts contained in other observations, as apart from the interpretation, 

 appear to agree perfectly with our own ; the result of which is, that in the fcetal state, car- 

 tilage is composed of a homogeneous matrix, in which lie the corpuscles, in cavities which 

 they just fill ; that their relation to the matrix is exactly that of the primordial utricles to 

 the cellulose wall in plants, and that like this they may or may not develop a nucleus ; that 

 with age they enlarge, but not so fast as the cavities, the walls of which become chemi- 

 cally altered into chondrin, a change which often takes place in such a manner as to give 

 rise to a lamination or to a difference in composition of the inner and outer portions. If the 

 cartilage be converted into fibro-cartilage, the outer part becomes changed into collagen, 

 while an alteration into a substance resembling elastic fibre, is effected in the inner portion, 

 and in the direction of certain lines radiating from it, just as we have seen the elastic ele- 

 ment to be developed in connective tissue (see on Connective Tissue). 



So much for the structure of cartilage: with regard to its development and multiplication 

 we must equally demur to the statements in the text. It is, indeed, very true, that no new 

 cartilage-cells arise independently of those which pre-exist: but in opposition to Professor 

 Kolliker we must agree with Leydig, Robin, Remak, and Tomes and De Morgan, that the 

 multiplication of the cartilage-cells invariably takes place by a process of division exactly 

 analogous to that which occurs in plants. So far as we have seen (and in ossifying carti- 

 lages, and in that of the Skate, it is easy to trace the process), the corpuscles first become con- 

 stricted, being found occasionally of an hour-glass shape; and eventually divide. The 

 matrix then grows in, so as to separate the two, and the process of fission is complete. TRS.] 



