BONE. 



49 



pecially near the circumference, which surround the whole 

 bone, and are arranged concentrically with regard to the 

 medullary canal. 



The ultimate structure of the lamellae appears to be reticular. 

 If a thin film be peeled off the surface of a bone from which 



FIG. 17. 



FIG. 18. 



FIG. 17. Haversian canals, seen in a longitudinal section of the compact tissue of 

 the shaft of one of the long bones. 1. Arterial canal ; 2. Venous canal ; 3. Dilatation 

 of another venous canal. 



FIG. 18. Thin layer peeled off from a softened bone, as it appears under a magni- 

 fying power of 400. This figure, which is intended to represent the reticular struc- 

 ture of a lamella, gives a better idea of the object when held rather farther off than 

 usual from the eye (from Sharpey). 



the earthy matter has been removed by acid, and examined 

 with a high power of the microscope, it will be found composed, 

 according to Sharpey, of a finely reticular structure, formed 

 apparently of very slender fibres decussating obliquely, but 

 coalescing at the points of intersection, as if here the fibres were 

 fused rather than woven together (Fig. 18). 



In many places these reticular lamellae are perforated by 

 tapering fibres, resembling in character the ordinary white or 

 rarely the elastic fibrous tissue, which bolt the neighboring 

 lamellae together, and may be drawn out when the latter are 

 torn asunder (Fig. 19). 



Bone is developed after two different fashions. In one, the 



