THE OSSEOUS SYSTEM. 



295 



:,.' f 



The lamellae of (he Haversian canals (fig. 112 c, L13 b) 

 surround those canals concentrically, in greater or less num- 

 ber. They constitute, as it were, 

 the walls of the canal, and are 

 intimately united to each other, 

 much in the same way that 

 the laminae of the walls of 

 the larger vessels arc con- 

 tinuous with each other. The 

 number of lamellae belonging 

 to a canal, and the collective 

 thickness of the system formed 

 by them, varies not inconsidera- 

 bly, and bears no constant re- 

 lation to the size of the canal, ( - ^^ 

 as is the case to some extent in 

 the vessels ; small canals, there- 

 fore, are not unfrequently sur- 

 rounded by numerous lamellae, " e 

 and larger ones by but few. 1 / 

 In general, it may be said, that 

 the largest canals have thin 

 walls, those of a middle size 

 thick ones, and the most minute, 

 again walls of little thickness. 

 The thinnest walls I have com- 

 monly noticed, measure 0008 " ^ 

 — 002"', and the thickest 008 *- ^ h 

 — - l'". The thickness of the lamellae varies between 0-002 

 and 0005'", being on the average 0-003 to 0001'"; in 

 number, there are usually from eight to fifteen ; sometimes, 



Fig. 112. Segment of a transverse section of a human metacarpal bone, treated 

 with oil of turpentine, x 90 diam.: a, external surface of the bone, with the exterior 

 fundamental lamellae; I, internal surface towards the medullary cavity, with the 

 inner lamellce; c, Haversian canals in transverse section with their lamellar systems ; 

 tl, interstitial lamellae; e, lacunae and processes. 



1 [The "interstitial laminae" are the remains of Haversian systems, the larger 

 parts of which have been removed by absorption to form new spaces. The irregular 

 outline of the outermost of the laminae of a Haversian canal (see fig. 113) results 

 from its being the first deposition within the pre-formed irregular Haversian space. 

 (Tomes and De Morgan, I.e., p. 5.) — Eds.] 



