10 



OSTEOLOGY. 



Fia. 3. 

 Longitudinal section of osseous 

 tissue, showing the arrangement of 

 the Haversian canals. 



or periosteal lameUcBy passing completely round tlie shaft. 

 There is also a corresponding concentric disposition of 



layers on the inner or medullary surface. 

 Both these systems of lamellaB are in a 

 great measure destitute of Haversian 

 canals, and are supplied with nutritive 

 material by means of lacunae and cana- 

 liculi, disposed as in the compact tissue 

 generally. 



The average diameter of the canaliculi 

 is TTjWth of an inch. The lacunae are 

 somewhat oval, and lie with their long 

 diameters, which measure about r»Wth 

 of an inch, parallel to the lamellae ; their 

 short diameter is about TmrTjth of an 

 inch. The compact tissue is therefore 

 copiously supplied with nutriment by 

 means of minute vessels, which enter from almost every conceiv- 

 able point. Each Haversian 

 canal may be considered a vas- 

 cular longitudinal centre, round 

 which successive concentric layers 

 of bone are arranged, so as to 

 form a dense cylindrical ossicle, 

 pjo ^ a Haversian System or Cylinder. 



Lacun» highly magnified, a, Cavity of Series of these are repeated, 



lacuna ; 6 6, The canaliculi ; those of the two -i -j. i i i n j j-j. i 



lacuna on the left are seen to join each other. ^^<^ United by lamellae destitute 



of canals, but with numerous 

 canaliculi and lacunae, and called the connecting or interstitial 

 lamellce, 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 Jluid 

 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 perios- 

 teum, and some even appear to be continued from inserted 

 tendons and ligaments. 



