THE CONNECTIVE TISSUES. 47 



opalescent, bluish tint of the hyaline variety. It is covered by a 

 perichondrium of the usual description. 



Fibro-cartilage, as implied by its name, is largely composed of 

 interlacing bundles of fibrous connective tissue, embedded in 

 which the round or oval cartilage-cells lie, singly or in groups, 

 immediatelysurrounded by a narrow zone of hyaline matrix. 

 TnenumDer ol the cells and the proportion of fibrous tissue present 

 differ in various specimens. 



Fibro-cartilage is found in comparatively few localities : around I J 

 the margin of articular surfaces and within certain joints, the sym- | 

 physes and the intervertebral disks, constitute its chief distribution. 

 The tissue is closely akin to tendon, presenting a white, tough, re- 

 sistant but pliable tissue. A proper perichondrium is wanting. 



The development of cartilage proceeds directly from the ele- 

 ments of the mesoderm. The primary close aggregation of the 

 embryonal cells, which early indicates the position of the future 

 cartilage, subsequently gives way to a looser disposition of the cells, 

 resulting from the appearance of the young matrix. After the 

 formation of the perichondrium, the cartilage grows by the addition 

 of new layers beneath the membrane. 



BONE. 



Bone is a dense form of connective tissue impregnated with lime 

 salts. Composed of the same histological elements as other compact 

 connective tissues, bone differs from these in having a deposit of 

 calcareous matter within the interfascicular 

 cement-substance, to which peculiarity the 

 well-known hardness of the tissue is due. 

 The microscopical appearance of bone 

 varies with the character of the prepara- 

 tion, especially as to whether the earthy 

 matter has been removed before sectioning, 

 or whether thin plates of dried bone are 

 examined ; it is in sections of dried bone 

 that the classical pictures of this tissue are 

 seen. 



Dependent upon the arrangement of the 

 matrix, two varieties of bone are recog- 

 nized spongy and compact. Although 

 the spongy bone is, as we shall see, the 

 fundamental form, yet the compact variety 

 alone presents all the structural peculiarities 



of the tissue. A transverse section of the compact osseous tissue 

 constituting the shaft of one of the long bones presents a number 



FIG. 53- 





Transverse section of dried bone : 

 k, one of the Haversian canals, 

 about which the lamellae are con- 

 centrically disposed, constituting 

 the Haversian systems ; g, the 

 ground or interstiti.il lamellae. 



