THE OSSEOUS SYSTEM. 309 



indication whatever afforded, of the production of cells independently of 

 those already in existence; and (2.) That the interstitial substance, 

 which in this case is manifestly formed, for the greater part, indepen- 

 dently of the cell membranes, is always increasing. With respect to 

 the cells, they are in the second costal cartilage of a four-month foetus, 

 according to Harting, 0-0036 of a line long, 0*0023 of a line wide, and 

 consequently their aggregate bulk pretty nearly corresponds with that 

 of the interstitial substance. In the embryo of the Pig, 3*5 lines long, 

 the space occupied by the nucleated, clear, thin-walled cells, is, accord- 

 ing to Schwann, thrice as great as that taken up by the interstitial sub- 

 stance. In a five-months' human embryo, I have myself noticed the 

 cartilage-cells, O'OOo-O-OOS of a line in diameter, with and without 

 secondary cells, some with, and some without distinct walls, and sepa- 

 rated from each other by a perfectly homogeneous substance, 0-002- 

 0-005 of a line thick. In the new-born child they measure, according 

 to Harting, 0-032-0028'"'" in length, and 0-0072'"'" in breadth, and are 

 three or four times as numerous as in the foetus at four months ; but on 

 the other hand, they occupy considerably less space, proportionally, 

 than the interstitial substance, the bulk constituted by which is more 

 than double that of the cells. After birth, in the non-ossifying carti- 

 lages, the interstitial substance and the cells increase in pretty nearly 

 an equal ratio, so that their relative proportions in the adult are about 

 the same as in the infant at birth. In the adult the cells are from 8 to 

 12 times larger than in the new-born child (Harting), but, according to 

 him, their number is diminished, so that they amount to not more than 

 half of what existed in the child, which is explained upon the supposition 

 of a coalescence of the cells. The numbers given by Harting do not 

 appear to me to afford sufficient ground for the establishment of his posi- 

 tion; and even should it be established, I cannot agree in the explana- 

 tion offered, not being aware of a single fact in favor of the notion of a 

 coalescence of cartilage cells.* 



* [We have deferred to this place the remarks we have to make with regard to the struc- 

 ture of the cartilage, and its mode of growth; as a just conception upon this subject appears 

 to us to be essentially necessary to a comprehension of the mode of development of Bone, — 

 in fact, we might say, to clear notions upon the structure of the tissues generally; for as we 

 shall show more at length below, it was upon the structure of cartilage, and what he 

 supposed to be its similarity to that of vegetable tissue, that Schwann based the whole 

 nomenclature of his cell theory. 



Now we may so far anticipate what we shall have to show hereafter, as to premise that 

 Schwann was misled upon two essential points, — the first being the supposition that the 

 histological elements of plants and animals are primarily independent, cells ; the second, the 

 notion that the " nucleus" of the animal, is homologous with the nucleus of the vegetable 

 tissue. It is, we believe, from the inextricable confusion produced by these fundamental 

 mistakes, which have been adopted by almost all Schwann's successors, that one-half of the 

 controversies with respect to the structureof cartilage and the process of ossification have 

 arisen. And yet to one who is free from them, nothing can be simpler. 



We have already (note p. 5G) referred to the structure of fcEtal cartilage, but it may here 



