268 



SPECIAL HISTOLOGY. 



sections of one of those bones, either parallel to the surface or perpen- 

 dicular to it, closely approximated canals running parallel to each 



Fi!?. 110. 



J] ivV\<^ 



c--' 



a' 



/ 



i 



! / \ity^ V 



i 



I 



\,r\ \ 





f- 



Y j'-'-'Sfctf 



\'VrJ:^A\ 





Fi?. 111. 



other, chiefly in a longitudinal direction, are seen, here and there ■with 

 connecting branches, and thus forming a network, consisting of elon- 

 gated, and most generally rectangular meshes (Fig. 111). And in a 



transverse section — transverse sections 

 of the canals, placed at tolerably defi- 

 nite but small distances apart, are prin- 

 cipally apparent (Fig. 112) ; which, 

 more especially in younger bones, are 

 occasionally connected by a tangential 

 branch, and some anastomoses in the 

 direction of the radius. In transverse 

 sections of foetal and undeveloped bone 

 (in man even at the age of eighteen),' 

 scarcely any transverse canals occur, 

 but chiefly those running horizontally 



Fig. 110. — Segment of a transverse section from the shaft of the /emrtr of an individual 18 

 years old : a, Haversian canals; 6, their openings internally; c, externally ; (i, osseous sub- 

 stance with lacunre. In this figure transverse sections of vascular canals and fundamental 

 lamelke are not shown. — Magnified 350 diameters. 



Fig. 111. — Haversian canals from the superficial lamellss of the /wmr of an individual 18 

 years old, treated with hydrochloric acid: a, canals; 6, osseous substance with lacunae. — 

 Magnified GO diameters. 



