XIII.] 



BONE, OSSEOUS TISSUE, ETC. 



181 



spherical mass of osseous tissue surrounds, and in fact is formed V.y, 

 each bone-corpuscle (fig. 154). There are thus spherical masses 

 cell-territories, as it were 

 and in the centre of 

 each a bone-corpuscle. 



7. Fibrillar Structure 

 of LamellsB (H). De- 

 calcify a bone in v. Ebner's 

 fluid (10-15 percent, sodic 

 chloride and 1-3 per cent, 

 hydrochloric acid). Either 

 this fluid or that given at 

 p. 3 7 may be used. Scrape i'i- 

 off a thin lamella and 

 examine it in water. 



(H) Observe the fibres of which it consists. They are com- 

 posed of fibrils arranged in bundles. They are best seen near 

 the edge. Fibres in different planes cross each other at a right 

 or obtuse angle. 



[ 54; 



-Simi'.lPartof Fi 



CC. Calcified 



L S- !53> 



cartilage; B. Bone; O. Osteoblast; BC. Bone- 

 corpuscles. 



ADDITIONAL EXERCISES. 



8. Blood-Vessels of Bone. These may be injected from the descending 

 aorta of a rabbit with a saturated and filtered watery solution of Briickc's 

 IVrliii blue. One must remember that the injection often fails. Inject from 

 the abdominal aorta, after a time using pretty high pressure. It is well 

 to ligature the inferior vena cava after some injection has flowed from it. 

 Decalcify the bone in chromic acid. The sections may be stained with very 

 dilute fuchsin. 



9. Decalcified Bone. Make a T.S. of dense bone rather a thick section 

 steep it in alcohol, transfer it to a slide, and mount it in glycerine-jelly, or in 

 a mor.-el of dry Canada balsam. In the latter rase the slide must be heated 

 to melt the balsam. Examine it at once, when the lacunae and canaliculi will 

 be seen black on a clear ground. They still contain air, hence their black 

 appearance. Gradually, however, the jelly penetrates into the canalicular 

 system, and ibis characteristic appearance vanishes, but it is an instructive 

 exercise for students to perform this experiment. Afterwards the lamella 1 

 remain quite distinct in the preparation, there are also faint indications of the 

 canaliculi. 



10. Bone in Polarised Light. Examine a non-decalcified transverse section 

 of the shaft of a long bone in polarised light (Lesson XVI. 16). When the 

 Nicols arc crossed, each llaversian system has a bright cross on a dark ground, 

 while ihe lamellse are alternately bright and dark. The crosses arc also seen 

 in decalcified bone, so that they arc produced by the organic basis or ossein 

 of the bone. 



