186 MANUAL OF HISTOLOGY. 



present (ekchondrosis), or a cartilaginous tumour may spring up in places 

 where cartilage does not normally appear, as, for instance, in bone or 

 glandular structures (enchondroma). In the latter, and not unfrequently 

 in the same tumour, we meet with the several varieties of cartilage as 

 regards its cells and interstitial substance ; islands of the true tissue are 

 sometimes separated from one another by fasciculi of connective- tissue. 



It now remains for us to consider the first appearance of cartilage in 

 the embryo, and the changes which take place in it subsequently. On 

 this point much valuable information has been contributed by Schwann, 

 Kolliker, Bmch, Heidenhain, and others. 



The histological development of cartilage takes place at a very early 

 period of intra-uterine life, as is indicated by the original simplicity of the 

 tissue, and its similarity to the first cellular rudiments of the organs and 

 various other parts of the system, namely, the embryonic cells. The first 

 anatomical rudiments of cartilage, that is, of the temporary tissue, appear at 

 the commencement whitish and clouded, without differing in texture from 

 the neighbouring structures. Its characteristic features begin, however, 

 to be developed very early. 



Originally these primitive cartilage cells lie closely crowded together, 

 and there is hardly the slightest trace of intermediate matter. The latter, 

 however, soon makes its appearance somewhat more distinctly. 



Thus, in the embryos of sheep, of 6-7 mm. in length, Kolliker found car- 

 tilage cells measuring -01 35-0 '0226 mm., and the intercellular substance 

 still very scanty. In larger embryos even, as those of the pig, of 2 

 inches long and upwards, the ground-substance is still much less in quan- 

 tity than the cells, in which latter the production of daughter-cells is be- 

 ginning. Fig. 175 represents this process. In other foetuses of the same 

 animal, measuring 3|- inches long, the intercellular substance amounts to 

 only about one-fourth of the whole volume, according to Schwann. At 

 the same time, the tissue is so soft that, on the slightest pressure, the 

 cells separate from one another, and float about in the surrounding fluid. 

 Later on, the proportion of the intercellular substance increases more and 

 more, while the cells enlarge, and endogenous multiplication reaches 

 in many cartilages a high degree of activity. But 

 during the growth of a cartilage, the number also of 

 the cells it contains increases by segmentation of those 

 previously existing. The stronger capsules, present- 

 ing different optical characters from the surrounding 

 medium, are only found at a later period of develop- 

 ment. Deposition of fats also (at least in the cartil- 

 ages of many new-born infants) may also be found 

 . 175. Carriage cells commencing (comp. fig. 165). The formation of 



from the body of aver- , , * " -L (i ui. -n , 



tebra of a foetal pig, of bands and appearance of chondrm fibrillation occurs 

 at a much later period. 



Great interest attaches to the discovery made by Schwann, and after- 

 wards confirmed by Hoppe, that the ground-substance of fcotal cartilage 

 does not consist originally of a matter yielding chondrin, or indeed of any 

 material which stiffens, like glutin, on cooling. 



All the statements just made refer, in the first place, to hyaline carti- 

 lage : the primary form of reticular and of fibro -cartilage, however, is also 

 included. The latter consist originally also of a homogeneous ground- 

 substance, in which the metamorphosis into fibres commences sooner or 

 later, and continues in some parts even after birth. 



