I '2 I ZOOLOGY. 



261. Of the Bones. To prove the presence of cartilage 

 as llif l;isis of all hones, all that is required is to iinn 

 hone in dilute nmriatir add, which, dissolving the calcareous 

 part, leaves a cartilage of the predse form and dimensions of 

 the bone itself. According to lierzelius, the bones of t In- 

 human skeleton are composed of cartilage, 32*17 ; vessels, 11*3 ; 

 phosj.hate of lime, with a little of the fluorate of calcium. 

 53*04; carbonate of lime, 11*30 ; phosphate of magnesia. 

 rii: soda, with a little of the chlorine of sodium, 1*2<> in 

 100*00 parts. The same chemist found the bones of the ox 

 to be similarly composed, but with much less carbonate of 

 lime. Thus bones by boiling afford much gelatine. 



The ossification of the skeleton commences with various 

 osseous points in the cartilages ; these are called nuclei or 

 germs. Jn youth they are numerous, but they gradually 

 coalesce ; thus the femur, in a young person, composed of 

 five distinct portions, is at last formed of one. In the lower 

 vertebrate animals many of those remain distinct, which in 

 the higher coalesce or become fused. 



The surface of bone is covered with a cellule-fibrous and 

 vascular membrane, called periosteum. The bones themselves 

 are composed of a compact tissue externally, and a cellular 

 and reticulated or cancellous internally. 



In the interior of the long bones are found cavities con- 

 taining marrow. The tissue itself, when examined under the 

 microscope, seems composed of tubes or cellules, surrounded 

 with concentric lamellae, between which may be seen opaque 

 ovoid corpuscles. 



262. The bones vary much in form, and anatomists 

 have divided them into long, short, and broad. Their sur- 

 faces present elevations (processes) and depressions, some of 

 which are for the attachment of muscles. 



263. Articulation of the Bones. By articulation is 

 meant the union of two or more bones ; they arc divided into 

 the immovable or fixed, and the moveable. The fixed m&y be 

 effected by juxtaposition, suture, and implantation; of the 

 first, certain bones of the face offer an example ; the bones of 

 the cranium unite chiefly by suture, and the teeth are fixed 

 into the alveoli by implantation ; this mode of articulation is 

 also called gompl 



264. In the moves-hie articulations, the bones are held 



in their place by ligaments maintaining them in juxtaposition. 



This bond of union is sometimes a fibro-cartilage, which 



