SECT. 91.] OSSEOUS SYSTEM. 173 



which, in virtue of Virchoiv's cells existing in them, the nutrient 

 fluid secreted from the vessels is conducted even iuto the densest 

 parts. 



The lacunae and their canaliculi do not present entirely the same 

 relations in all parts of the bones. In the lamelhe round the 

 Haversian canals, the elongated lacunas, when viewed in transverse 

 sections (fig. 77), are, by reason of their curvature, arranged, as it 

 Mere, concentrically ; and their very numerous canaliculi give rise 

 to a very close striation radiating from the vascular canals. The 

 lacunae arc sometimes ex- Fitr 78- 



tremelv numerous, sometimes 

 more sparing; in the former 

 case, they alternate with to- 

 lerable regularity, or are dis- ^ ; ;§*ijtl' jijwi^ '-%*£ '*M 

 posed in succession in the -i#^^| j|'%|v*'v>-^'- i i' , 'ffi-: 

 direction of the radii of the V^Vf^m^0'^ih -^& 

 concentric lamellae; but fre- ^JU'^JpUfi ; W^ ; > <■■ '$*•*■*•{% 



quently they are arranged *Vfpl^bl&J MpM '4*>'**| 

 very irregularly, collected in t$t,£ pli • % \*f^^^'§ %l^*k 

 heaps, or separated by larger :| -^ ,^ ,/?,->< f- 



intervals. In longitudinal 0&*J' r 'fr£-A%% : $J 



*t> 



c 



H'J rJo :.i *■ 



sections of Haversian canals #^ '';'/: rt I |)t 



(fig. 78), the lacunae are seen '''^t-&$&\ WS^ / / ^R^^ 



as narrow elongated objects, ^ lb*J ( '^' ;> ;V^| 



arranged in linear series and *^ t -/'I^M ; || ;<iHy. ^fCtt^"^*^''^ 



disposed in several layers pa- X ./ ^-^i ; |^%^^|^***-"^ 

 rallel to the canals. They % fe^^^it *: 



are likewise provided with nu- vlf „<;•%! \u$y*£\X&ii.-?* 

 merous canaliculi, which pass, * %-":0! fMi f"^ v ^ ?; f s! 



for the most part, directly in- * i * * ** "U f > 



Wards and outwards (there- ffi ■■* ; --%-" '""*>lf 



fore transversely through the Section para i lel t0 the surface) from tho dia . 



LiitipIIt^ nnrl n «mnllpr nftH-inn P h J' sis ot ' a human femur; magnified 100 times. 



lauiLlULj, dUU a Smaiiei pOlllOU a Haversian canals; 6. lacunaj seen from the side, 



navnllrl tn flip lnnrr ivic r>f belonging to the lamellae of the same ; c. others seen 



prtidllLl IO LUC XOUg aXIS OI from tbe BUrfacej m i ame llse which are cut hori- 



the canals. If the section zontaIly " 



happens to fall on the surface of a system of lamellae, the lacunae 

 are seen flatways, and then appear in the form of beautiful 

 rounded, or oval, or irregularly outlined bodies, with tufts of 

 canaliculi (fig. 79), which are directed towards the observer, 

 and, consecmently, appear more or less foreshortened, whilst 

 a small number of others run along the lamellae. In the 

 thinnest parts of a section, there is seen occasionally a tuft of 



