10 



OSTEOLOGY. 



are several concentric osseous layers, the peripheral or periosieal 

 lamellce, passing completely round the shaft. There is also a 

 corresponding concentric disposition of layers on the inner or 



medullary surface. Both these systems 

 of lamellae are in a great measure 

 destitute of Haversian canals, and are 

 supplied with nutritive material by 

 means of lacunae and canaliculi, disposed 

 as in the compact tissue generally. 



The average diameter of the canaliculi 

 is Twirth. of an inch. The lacunae are 

 somewhat oval, and lie with their lo-ng 

 diameters, which measure about -jsVirth 

 of an inch, parallel to the lamellae ; their 

 short diameter is about TfeVoth of an 

 Longitudinal section of osseous inch. The compact tissue is therefore 



tissue, showing the arrangement of i v i -,i , i 



the Haversian ranai* copiously supplied with nutriment by 



means of minute vessels, which enter 



from almost every conceivable point. Each Haversian canal 



may be considered a vascular 

 longitudinal centre, round which 

 successive concentric layers of 

 bone are arranged, so as to form 

 a dense cylindrical ossicle, a 

 Haversian System or Cylinder. 

 Series of these are repeated, and 

 Lacunas highly maunititd. >,, Cavity of united by lamellae destitute of 



lacuna ; 6 b. The canaliculi ; those of the two pnna l, hilt with numerous Cana- 

 lacuiiiB on the left are seen to join each other. 11S C 



liculi and lacunae, and called the 



connecting or i)ttcrstitud lamelLcB, the entire structure being 

 encircled by the external peripheral lamellae, thus constituting 

 the compact tissue, and in such a way as to combine strength 

 and density with efficient nutrition, the nutritive material being 

 conveyed by the canals, canaliculi, and lacunae ; the last two only 

 transmit the fluid portion of the blood. The canaliculi interlace, 

 and some pass directly through the lamellae to the central 

 Haversian canal. The lamellae are in places pierced, and, as it 

 were, pinned together by fibres, or fibrous bundles known as the 

 perforating fibres of Sharpey; some of these are derived from the 

 periosteum, and some even appear to be continued from inserted 

 tendons and ligaments. 



Fin. 4. 



