108 LECTURE IV. 



nutrition upon the juice which exudes from the terminal 

 loops and permeates the tissue, though to a trifling ex- 

 tent also upon the materials which the scanty vessels of 

 the perichondrium convey to it. The vessels which 

 spring from the nutrient artery mark in all bones, at a 

 tolerably early period, pretty exactly the limits to which 

 the ossification subsequently proceeds, whilst the rem- 

 nants of the cartilage which remain bordering upon the 

 joint never contain vessels. 



With regard to the bones themselves, the disposition 

 of their blood-vessels is in itself tolerably simple, but at 



FIG. 32. 



the same time very characteristic. If we examine the 

 compact substance, we can usually, even with the naked 

 eye, distinguish upon its surface small openings through 

 which vessels enter from the periosteum. With a mode- 

 Fig. 32. Longitudinal section from the cortex of a sclerotic tibia, a, a. Medullary 

 (vascular [Haversian]) canals, between them the bone-corpuscles for the most part 

 parallel ; but at b (in transverse section) concentrically arranged. 80 diameters. 



