SECT. 90.] 



OSSEOUS SYSTEM. 



169 



and in the bone-cartilage can also be raised up with the forceps. 

 In the middle part of the cylindrical bones, they form two 



systems, a general, which runs 

 inner surfaces of the bones, 

 and many special, surrounding 

 the separate Haversian canals. 

 These systems, it is true, are in 

 many places immediately con- 

 nected with each other, but, for 

 the most part, are only in appo- 

 sition, and can, therefore, be c 

 conveniently regarded as being 

 of two kinds, which view is also 

 to some degree supported by their 

 mode of development. 



The lamellae of the Haversian 

 canals (fig. 76) surround those 

 channels concentrically, in greater 

 or less number. They form, as it 



parallel to the outer and 



Pig. Tfi 



■r 



c£ 





•C^- 



were, their walls, and are con- 



a similar 



Segment of a transverse section of a human 

 metacarpal bone, treated with concentrated oil of 

 turpentine; magnified 90 times, a. Inner surface 



nected with each in 



Wav as tllP 1 avers nf flip "svfllk nf ? f thebone > with th e inner fundamental lamella;; 

 h.iv as lilt, UV\tlS OI tne WailS OI 6 . transverse section of the Haversian canals, 



thf lnro-pr vpsspIs Tn o-ptipviI tIip with tlleil " lamellar systems: c. interstitial la- 



liiu iai s ei v e^uiu. xn genei ai, tne meUse . d _ lacuna , and their processes . 

 widest canals have the thinnest 



walls; those of middling size, thicker; and the narrowest, again, 

 less thick walls. The thinnest walls which I have in general seen 

 amounted to o-oo8'" to 0-02'" in thickness; the thickest, croS'" to 

 01'". The thickness of the larnelke varies between 0-002'" and 

 0005'", and is, on an average, from 0-003'" to 0-004'"; their, 

 number is, as a rule, 8 to 15, but may not exceed 4 or 5, or 

 may amount even to 18 or 22. 



The lamellae of the Haversian canals extend, with the canals to 

 which they pertain, to the inner and outer surface of the diaphyses, 

 and are here connected with the above-mentioned general lamellae, 

 the fundamental lamince, which form an outer and an inner layer, 

 and which, besides, penetrate into the diaphyses between the special 

 systems of lamellae round the Haversian medullary canals (inter- 

 stitial layers). The former two layers, or the outer and inner 

 fundamental lamella, run parallel to the outer and inner surfaces 

 of the bone, and vary in their thickness from 0-02'" to 0-3'", or 

 even to 0-4'". The latter, or the interstitial fundamental lamella?, 

 where the superficial fundamental lamellae are developed, are most 



