ON THE INTIMATE STRUCTURE OF BONE. 31 



Fig. 5.* 



In the transverse section, each of the orifices of the canals, 

 Fig. 5, is seen surrounded by ten or fifteen concentric lines, 

 which on examining the longitudinal section, Fig. 4, are found 

 to be as many lamellae running the whole length of the canal, 

 and each about the ? | 5 th part of an inch in diameter, accord- 

 ing to the microscopical measurement of Deutsch.f The spaces 

 in the transverse section of the bone, not occupied by the lon- 

 gitudinal canals and their concentric lamellae, are filled by 

 other lamellae, which form larger concentric rings round the 

 great medullary cavity. The diameter of the canals of Havers, 

 according to Miescher, varies from ^th to ^ili of an Eng- 

 lish inch. 



In the flat bones the canals with their lamella, run parallel 

 with the surface of the bone. In the long bones, the longitu- 

 dinal canals are directed obliquely into the central cavity. 

 In the lamellae concentric to the canals, there is an appear- 

 ance of dots or short lines, which do not occupy the whole 



* Fig. 5. Is a transverse section of one of the flat bones of the cranium, mag- 

 nified one hundred times, a. Compact substance or table of bone, expanding 

 into diploe. b. b. c. c. Vasculo-medullary canals of the compact portion, cut 

 across, d. Transverse communicating canals, between these and the larger 

 canals or cellular cavities of the diploe. e. Diploic cells communicating with 

 others at /. Diploic cells like the canals of the compact portion, are surrounded 

 with concentric striae or lamellae, and are in fact only amplified vasculo-medul- 

 lary canals. The spots upon the surface, are the bony corpuscles. 



f Some modern observers have made the diameter or thickness of each of 

 these lamellae, much less than that stated by Deutsch. Mr. Wilson states it to 

 be not more than the ^5^ a measurement which appears to me to err much 

 on the minimum side . 



