456 LECTURE XVIII. 



attains, essentially depends upon the extent to which 

 growth occurs in the individual groups of cartilage -cells. 

 Whether we ultimately become tall or short, is, if I may 

 say so, left entirely to the discretion of these elements. 

 When the growth of the proliferating cartilage has 

 reached this point, the cellular elements are very close 

 together, so that a comparatively trifling quantity of 

 intercellular substance lies between them (Fig. J.24). 

 The farther the development advances, the more does 

 the appearance of the cartilage alter, and at last it looks 

 almost like dense-celled vegetable tissue. The cells 

 themselves however are difficult to be seen, because they 

 are extremely sensitive ; they readily shrivel up upon 

 the addition of the mildest fluids and then appear like 

 angular and jagged corpuscles, almost analogous to those 

 of bone, with which however they have at this time 

 nothing to do. 



The cells which have sprung from this excessive proli- 

 feration of the originally simple cartilage cells, consti- 

 tute the parent structures from which proceeds all that 

 afterwards arises in the longitudinal axis of the bone, 

 and especially the osseous and medullary tissue. The 

 cartilage-cells may be converted by a direct transforma- 

 tion into marrow-cells and continue as such ; or they 

 may first be converted into osseous, and then into me- 

 dullary, tissue ; or lastly they may first be converted 

 into marrow and then into bone. So variable are the 

 permutations of these tissues in themselves so nearly 

 allied, and yet in their external appearance so com- 

 pletely distinct. When a direct transformation into 

 marrow is the first effected, the old intercellular sub- 

 stance of the cartilage at the border next to the bone 

 begins first of all to grow soft ; then some of the ad- 

 joining capsules usually also very soon experience this 

 change, so that the cellular elements come to be more 



