OSSIFICATION IN CARTILAGE. 481 



tance to the cellular theory in general. In this speci- 

 men (Fig. 134) the whole series of these processes is 

 seen at a glance. Where the completely ossified por- 

 tion, in which the bone-corpuscles are developed with 

 perfect regularity, adjoins the cartilage, you see a zone 

 where the conversion of cartilage -corpuscles into perfect 

 osseous substance may be viewed within the limits of a 

 very short space. At the point of transition a number 

 of corpuscles are found lying close to one another like 

 hazel-nuts distinguished from ordinary cartilage-cor- 

 puscles by their dark contours, hard appearance, and 

 unusually great brilliancy, and enclosing in a small, 

 indented cavity a little cell ; these little cells are the 

 still isolated* bone-corpuscles with calcified capsules 

 which they have retained from that earlier period in 

 their existence when they were cartilage-cells. It is 

 especially important that you should see these bodies 

 thus isolated in situ, in order that you may compre- 

 hend those other processes, in which in bone the terri- 

 toriesf belonging to the bone-cells fall out (p. 462, Fig. 

 129). When an object of this kind has once been accu- 

 rately examined, it is impossible that doubts can any 

 longer arise as to whether cartilage -cells can become 

 bone-corpuscles, and I cannot conceive how it is that 

 even the most recent (and those very careful) observers 

 still start the question, whether bone-corpuscles are not 

 in all cases structures obtained by a circuitous route, and 

 not directly produced from cartilage-corpuscles. It is 



* Isolated, because their capsules have not yet become fused with the basis-sub- 

 stance. From a MS. Note by the Author. 



| In bone formed directly (i. e., without the intervention of medullary tissue) out 

 of cartilage, the territories of the bone-cells correspond to the cartilage-capsules. 

 But when bone is developed out of any other tissue, the limits of these territories 

 cannot be distinguished at all during growth, and it is only when gaps arise (through 

 disease) in the bone around the bone-cells that these limits are defined. From a 

 MS. Note by the Author. 



31 



