18 PROCEEDINGS OF THE AMERICAN ACADEMY 



Two varieties, however, dependent upon degree of organization, are 

 met with : — 



" The first is cellular cartilage, being of a transient nature, ulti- 

 mately to be (Ranged into bone. It is composed of nucleated, well- 

 defined cells lying in a semi-solid, punctiform stroma. 



" The second is Jibro-cartilage of a permanent nature, and consist- 

 ing of the same cells as the first, but which lie in a network of 

 fibrous tissue, which last is only a further developed condition of the 

 punctiform stroma. 



" In fibro-cartilage the fibrous tissue may so increase at the expense 

 of the cellular elements, that these last almost entirely disappear, and 

 hence the transition of fibro-cartilage into fibrous tissue. 



" From this it will appear that all cartilage is originally the same, 

 that is, cellular, appearing as such in the embryo. 



" Its formation there, according to my own observation, occurs in 

 the following manner. 



" At those points where cartilage and afterwards bone is to appear, 

 there are seen cells which, as to physical characteristics, cannot be 

 distinguished from those which are to form other tissues. 



" A part of these cells are condensed into a punctiform stroma, 

 leaving open spaces here and there, in which the original cells in 

 numbers from one to four remain. Thus is ultimately seen a finely 

 granular stroma, inclosing free nucleated cells. This is the true 

 cellular cartilage. 



" As this stroma is formed closely about the cells, it is not correct 

 to say that cavities are formed in it, and in which the cells lie. For 

 the cell-membrane, lying in direct contact with the stroma, blends with 

 it, the nuclei alone, therefore, being left in the cavity ; but as these are 

 nucleolated, they resemble cells, and should be thus designated. 



" \n jibro-cartilage the same early changes occur, but the stroma is 

 further developed into a fibrous or fibrillated tissue. Where this has 

 occurred, the cell-nuclei lie in nidiform cavities. 



" Cellular cartilage alone is developed into bone. This occurs in 

 the following manner. When the ossific matter is about to be de- 

 posited, the vascularity of the cartilage is much increased, having 

 a pinkish hue. Then a kind of liquefaction of the stroma interven- 

 ing the cells takes place, by which the cartilage-cells appear no 

 longer confined irregularly, but are, for the most part, free to assume 

 any relative position. Soon after this, there is seen with them a ten- 



