COMPARATIVE RETROSPECT. 107 



It is easy to see -which elements of the tissues of this and 

 the preceding class correspond. There the whole tissue 

 consisted of cells, closely crowded together, and the in- 

 tercellular substance was almost nil. Here we find the like 

 arrangement only in the lowest stage of development of the 

 most simple cartilages. In such as are more highly developed, 

 those of all the mammalia for example, the cells lie surrounded 

 by a larger quantity of intercellular substance, which fun us 

 the proper cartilaginous substance ; but the cell-walls contri- 

 bute onlv verv slightly, or not at all, to its formation. The 

 proper firm substance of these higher cartilages, therefore, has 

 its analogy in the former class, only in the minimum of cyto- 

 blastema by which the cells are connected, while, on the other 

 hand, it corresponds with that which, in the first class, was 

 the fluid, wherein the isolated cells were formed. The carti- 

 lage-cells in this class, however, correspond precisely to the 

 epithelium-cells, the feather-cells, &c. &c, in the preceding 

 one, and the blood-corpuscles, mucus-corpuscles, &c. in the 

 first class. 



We have not found any new changes in the form of the 

 cells in this class. Most of them were angular, somewhat 

 approaching the circular form ; and stellated cells, so far at 

 least as we may be permitted to regard the osseous corpuscles 

 as such, were also frequently met with. (See pp. 29, 30.) 

 Some cells, which were remarkably elongated, were observed 

 near to the surface of several cartilages, in which situation 

 they are known as greatly elongated cartilage- corpuscles ; 

 still, however, this appearance is never presented by the cells 

 of this class in so remarkable a degree as it is by those 

 of the crystalline lens in the previous one. The fibro- 

 cartilages, on the other hand, form the immediate transition 

 from this to the following class, for in them a bundle of fibres 

 seems to be formed out of each cartilage-corpuscle, a process 

 which we shall consider more minutely when treating of cel- 

 lular (areolar) tissue in the next class. 



AVc have observed the formation of cells around the pre- 

 viously-existing nucleus, and their progressive growth, goin Li- 

 on in this class in a similar manner to that exhibited in the 

 preceding, and the true cartilage-cells were also seen to form 

 around a cvtoblast which lav external to the cells already 



