G EN ERA L UISTOL G Y. 



87 







^' ' -'^-"^'y^ 



glutin, so iutimiitely coinbinod with inorganic constituents tliat it 

 appears nnder the microseoiJe as 

 a homogeneous mass. The propor- 

 tion of organic and inorganic sub- 

 stances varies according to the age 

 and sp)ecies of animal : in man, for 

 example, there is 05^ inorganic to 

 35^ organic suljstanee; in the 

 turtle, Gofo to 37^. Of the in- 

 organic constituents, the most im- 

 portant is calcic phosphate, 84^; 

 in smaller quantities, combinations 



of fluoric, chloric, carbonic acids i^, , ^ ^-,-t ^^^%,^^^^ j,-)- 

 and magnesia. Morphologically f J^^^/%: '' 'K'''^r''^:^'l V^ 

 the matrix is composed of the bone ^ •' '^ — ' ^'^ -^ ''< "^-^ 

 lamella3 (fig. 44), whose arrange- 

 ment is determined fiy the surfaces 

 present in and upon the bone. In 

 a hollow bone (like that of the 

 upper arm or of the hand) there is 

 an outer surface to which a fibrous 

 skin, the bone-skin or periosieuni, 

 is closely applied; the presence of 

 the marrow-cavity necessitates a 

 second surface. Finally, the solid 

 mass of the bone is permeated by 

 the Haversian canals, which run 

 chiefly in a longitudinal direction, 

 united into a network by cross or 

 oblique canals, and serve for the 

 passage of blood-vessels. Since the 

 bone lamella3 arrange themselves 

 parallel to the surfaces mentioned, two systems may be distin- 

 guished in cross-section, the fundamental lamellaj and the 

 Haversian lame]l;>i. The former are arranged jjarallel to the sur- 

 face of the iieriosteum ami of the marrow-cavity and form a 

 mantle of concentric layers around the marrow-cavity. Inti^i this 

 groundwork the Haversian canals with their lamel]a3 enter, 

 destroying and suiierseding the fundamental lamella; coming in 

 their way. 'i'he Haversian lan^ellaj are concentrically arranged 

 around the lumen of the Haversian canals just as tlie fundainental 

 lamello3 are around the marrow-cavitv. 



Fig. i4. — Cro^s-section 1hr<tui^li tlie 

 liuman metacai'ijus. ( Afri.-r Fivy.l a, 

 surface of the periosteum; h, surface 

 of the marrow-cavity; c, cross-sec- 

 tions of the Haversian canals and 

 their system of lamellae ; d, funda- 

 mental himeUte; f, bone corpuscles. 



