THE OSSEOUS SYSTEM. 373 



with ov.il nuclei of 0-0028 — 0-00-18"'. Such of these cells as 

 are destined for the growth of the bone in thickness, with the 

 exception of those of the glenoid cavity of the temporal bone, 

 never present the slightest resemblance to cartilage-cells, and, 

 together with their matrix, invariably ossify without the 

 appearance of any calcareous particles ; those on the borders 

 or extremities, on the contrary, may, as it appears, subsequently, 

 take on the nature of true cartilage. The most striking 

 example of this kind occurs in the condyle of the inferior 

 maxilla, where, even during fcetal life, a thick cartilaginous 

 layer is deposited, which so long as the growth of the bone 

 continues, precedes its longitudinal growth, exactly like an 

 epiphysal cartilage. I have noticed the same thing in the 

 articular fossa of the temporal bone, where, however, the 

 cartilage is less developed; at the angle of the inferior maxilla 

 (in the Calf), and at the anterior extremities of each half of 

 the same bone, which are connected by a semi-fibrous, semi- 

 cartilaginous substance, corresponding very nearly with the 

 symphysis. This fact loses much of the singularity which at 

 first sight attaches to it, when we consider that all cartilage 

 is at first soft, and consists of common formative cells. It is, 

 consequently, only necessary, that the formative cells of the soft 

 blastema of the secondary bones, should, at a certain period, 

 pass through the same changes as those undergone by the 

 formative cells of embryonic cartilage, in order to effect the 

 production of cartilage in the bones now in question. Further 

 investigation is required to show, whether cartilage of this 

 kind also occurs as a supplementary addition to other secondary 

 bones, and to what extent, in animals. Still, it may be noticed, 

 that in asserting as I have done, that all ossifications from a 

 soft blastema take place without the deposition of calcareous 

 granules, this statement is only in part correct, because it is 

 quite true, in many cases, that this sort of deposition does 

 occur in them, though never at an early period, and, generally 

 speaking, but rarely. The ossifyiug margin, moreover, in these 

 cases is never abrupt, as it is in ossifying cartilage. 



The ultimate changes of the secondarv bones have not vet 

 been closely investigated. Their mode of connection with 

 each other, and also with primary bones by suture and 

 coalescence, is tolerablv well known. In the vault of the 



