62 CONNECTIVE TISSUES. 



formerty used, which consisted in staining sections of cartilage, 

 previously steeped in chromic acid solution, may be dispensed 

 with ; the plan above recommended possessing the great ad- 

 vantage over it, that the cartilage cells retain their natural 

 form completely. Before leaving hyaline cartilage a word 

 must be said as to the arrangement of the cells in the carti 

 lages which occupy the centre of the epiphysis of the tibia ot 

 the frog. If the tibia of a frog is enucleated from the knee- 

 joint, and sections are made at right angles to the axis of the 

 bone through the condyles, these exhibit concentric layers, 

 arranged around two centres corresponding to the two con- 

 dyles. Proceeding from without inwards, we have first articu- 

 lar cartilage, then an external periosteum, a ring of bone, an 

 internal periosteum, and, finally, a nucleus of cartilage on 

 either side, one corresponding to each condyle. These two 

 cartilages are hyaline, but each cell constitutes a rigid lamina, 

 which is separated from its neighbors by little or no matrix. 

 Towards the diaphyses each nucleus tapers away gradually ; 

 and, in its lower part there is a cavity which is continuous 

 with the medullary cavit} r of the diaphysis, and contains a 

 little liquid. The cells are here more separated from each 

 other than they are towards the condyles ; but, immediately 

 round the cavity, they are more densety arranged, are roundish 

 in form, and look like lymph corpuscles, consisting of finely 

 granular protoplasm. 



In embryonal cartilage, the spindle-shaped or stellate branch- 

 ed cartilage cells, which consist of granular protoplasm, and 

 possess spheroidal nuclei, are crowded together in a hyaline 

 substance, penetrated throughout \>y bloodvessels (e.g., in the 

 patella or head of the femur of the human foetus). In the 

 immediate neighborhood of the vessels they possess more or 

 less the form of ordinary cartilage cells. They may be 

 prepared for observation in the same way as the others. 



Yellow Cartilage differs from hyaline in the fact that its 

 matrix consists of a network of elastic fibres, in which there 

 are cavities occupied by cartilage cells, either isolated or in 

 groups. These are sometimes surrounded by a certain quan- 

 tity of hyaline substance. The best objects for the study of 

 this tissue are the epiglottis and the cartilage of the external 

 ear ; these may be examined fresh or in chloride of gold. In 

 addition to these forms, the so-called parenchymatous cartilage 

 must be mentioned ; i. e., cartilage without matrix. This 

 occurs in the embryonal chorda dorsalis, and in the tcndo 

 Achilles of the frog. We have already studied an example of 

 it in the nucleus cartilage of the epiphyses of the frog's tibia. 



Fibro-Cartilage. In fibro-cartilage the structural ele- 

 ments of cartilage are intermixed with gelatigenous tissue, as 

 in the neighborhood of the insertions of tendons into bones, in 



