296 



SPECIAL HISTOLOGY. 



however, no more tlian four or five, and occasionally as many 



as from eighteen to twentv-two. 

 The lamellae of the 



Fig. 113. 



Haversian canals, together with 

 their canals, extend 

 to the internal and 

 external surfaces of 

 the diaphyses, where 

 they are connected 

 with the general 

 lamellae above men- 

 tioned — the funda- 

 mental lamella (fig. 

 111). The latter con- 

 stitute an external 

 and an internal laver, 

 and penetrate also 

 into the substance 

 of the diaphysis, 

 where they are in- 

 terposed between the 

 separate lamellar sys- 

 tems and the me- 

 dullary canals. The 

 two former layers, or 

 the external and in- 

 ternal fundamental lamella, are parallel to the external and 

 internal surfaces of the bone, and vary in thickness appa- 

 rently without any definite rule, from 002" to # 3'", or even 

 0*4'". The latter, or interstitial fundamental lamella, are seen 

 most clearly where the superficial fundamental laminae are 

 developed, in partial connection and parallel with which they 

 extend from without inwards, and from within outwards, some 

 distance into the substance of the diaphyses, where they are 

 interposed in masses, varying in thickness from 002 to 012"', 



Fig. 113. Portion of a transverse section of the shaft of the humerus, x 350 

 iliam., treated with oil of turpentine : «, Haversian canals; b, their lamellar systems, 

 each lamella presenting a more transparent and more opaque portion, with radiating 

 striae in the latter; c, darker lines, which probably indicate greater intermissions in 

 the deposition of the osseous substance ; d, lacuna? without visible rays. From a 

 preparation by Dr. 11. Midler. 



