CONNECTIVE TISSUE. 



233 



puscles are sometimes sharply marked. Into the intermediate 

 bone-tissue we can also trace vascular canals the lateral 

 branches of the longitudinal vessels of the compact bone. 



In the tibia of a dog several years old, the area of the bone- 

 tissue surpasses that of the vascular canals by twelve or fifteen 

 linear diameters. Large medullary spaces are found only near 

 the central marrow-tube, while the rest of the cortex exhibits 

 vascular canals of varying calibers, the larger of which contain 

 some reticular connective tissue and fat-globules around the 

 vessel. The parallel systems of lamellae belong either to a single 

 vascular canal or to two or three narrower systems which are 

 surrounded by a large common system. The intermediate tissue 

 is usually lamellated ; in portions where lamellae are wanting, 

 semicircular or circular contours of territories are found surround- 



FIG. 92. TIBIA OF A DOG, TEN YEARS OLD. TRANSVERSE SECTION. 

 CHROMIC ACID SPECIMEN. 



S, system of lamellae with a central vascular canal ; O, system of lamellae with a central 

 bone-corpuscle ; J, intermediate lamellated bone-tissue. Magnified 200 diameters. 



ing small, bay-like spaces. Not infrequently we meet with sys- 

 tems of lamellae, the centers of which are not occupied by a vas- 

 cular canal, but by a bone-corpuscle. 



Similar conditions are found in the tibia of a dog eight to 

 ten years old, although the solid systems of lamellae are still more 

 numerous. The central marrow-tube is inclosed by a common 

 lamellated bone-layer, while the layer between the periosteum 

 and the bone is lamellated only in part. (See Fig. 92.) 



The femur of the same animal is encircled by a broad, lamel- 



