232 



CONNECTIVE TISSUE. 



cms than medullary spaces, however, are the so-called " vascular 

 canals " /. e., cylindrical or oval tubes, with one or two much 

 elongated blood-vessels, and oblong or spindle-shaped medullary 

 corpuscles. The larger the diameter of a medullary space or a 

 vascular canal, the narrower, as a rule, is the surrounding bony 

 layer 5 the broadest layers of lamellae correspond to the narrow- 

 est vascular canals. The blood-vessels of the medullary spaces 

 anastomose with those of the vascular canals by means of trans- 

 verse and oblique branches 5 the vessels of the canals anastomose 

 with each other, and with every vessel we find a varying thick- 

 ness of lamellae. (See Fig. 91.) 



In the diaphysis of the tibia of a dog a little over a year old, 

 the area of the bone-tissue surpasses that of the vascular canals, in 



FIG. 91. TIBIA OF A DOG, Six MONTHS OLD. TRANSVERSE SECTION. 

 CHROMIC ACID SPECIMEN. 



M, medullary space, with a relatively small amount of surrounding lamellas ; Si, narrow 

 system of lamellae around a medullary space; /S 2 , broader system around a vascular canal. 

 Between the systems is the lamellated intermediate hone-tissue. Magnified 200 diameters. 



a linear direction, six to eight times. In the compact bone, larger 

 medullary spaces are found only in the vicinity of the central 

 marrow-canal. The vascular canals are surrounded by broad 

 systems of lamellae, containing the bone-corpuscles in a concen- 

 tric arrangement. Sometimes we meet, in transverse sections, 

 with two smaller systems, each with a central canal, -the two 

 encircled by a common layer of an hour-glass shape. The inter- 

 stices between the systems are filled by a non-lamellated bone- 

 tissue, whose corpuscles are somewhat larger than those of the 

 lamellae, and irregularly distributed. The territories of such cor- 



