46 ANATOMY. 



which are fixed to the breast-bone, the matrix is indistinctly striated. 

 The cartilages of the ribs and larynx become bony in old age. 



Fig. 21. 



Fig. 21, a, a small piece of articular cartilage, from a joint, showing its solid matrix and the cartilage 

 cells, with their little contained nuclei, embedded in it. b, portion of white fibro-cartilage, consisting of 

 nucleated cartilage cells, embedded in a somewhat fibrous matrix. Magnified 260 diameters, (a, Sharpey. 

 6, Kolliker.) 



Fibro-cartilage may be regarded as a mixture of cartilage and fibrous 

 tissue, or as a cartilage with a distinctly fibrous matrix, containing 

 cartilage-corpuscles and nuclei, Fig. 21, b. It is found in certain joints, 

 as will be hereafter explained. 



In yellow fibro-cartilage, the fibrous part is soft and resembles elastic 

 tissue. Examples of it are found in the ear, eyelids, and valve-like 

 epiglottis. 



Articular cartilage is absolutely without bloodvessels, i. e., is non- 

 vascular. The other kinds are all slightly vascular ; and they also 

 have a fibrous membrane investing them called the perichondrium, 

 which is vascular. No nerves have been seen in them. 



Osseous tissue or bone. The outer so-called compact tissue of bone 

 is not quite solid, but is traversed by minute tubes called the canals of 

 Havers, which form a longitudinal network in the bone-substance, and 

 open by minute pores on the surface. The finest canals are near the 

 surface of the bone : further in, they get larger and at length open 

 into obvious channels, which becoming still wider, form at length the 

 cancelli of the spongy tissue, which finally merge, at least in the long 

 bones, into the central cavity for the marrow or medullary cavity, Fig. 

 22, a. When more highly magnified, b, and Fig. 23, the bony sub- 

 stance surrounding these canals and cancelli, is seen to be arranged in 

 concentric laminae firmly united together, and having lying between 

 them very minute cavities called the lacuncp of bone or bone corpuscles, 

 from which numbers of exceedingly fine tubuli called canaliculi, pass 

 into the solid substance of the laminae, and connect neighboring lacu- 

 nae and Haversian canals. In the living state, the Haversian canals 

 are occupied by small often capillary bloodvessels, which enter the 

 bone from the periosteum, and communicate also with the bloodvessels 

 of the marrow. Bone is therefore a very vascular tissue ; most of its 

 vessels reach it from the periosteum ; but in the long bones, there is 

 usually an artery for the medulla which enters the bone by a distinct 

 orifice. A nerve enters at the same opening ; but bone is not sensi- 

 tive unless inflamed. 



Dry bone consists of two-thirds of earthy matter and one-third of 





