120 J. SLADE ON PREPARING SECTIONS OP BONE AND TEETH 



"■ Human Microscopic Anatomy," I have gained by successes and 

 failures a certain amount of experience, ■whicli I now bring here in 

 order to be criticised and discussed by any one who may have been 

 at work upon the same subject. 



Bone, under a power of from 50 to 100 diameters, shows the 

 Haversian canals, with the bone in laminje surrounding them ; 

 under 200 or 300 diameters, that which appeared before merely as 

 black specks, turns out to be the spaces with radiating lines known 

 as "lacunae" and " canaliculi. " These lacunae and canaliculi vary 

 in size and form, and are in a general way characteristic of the 

 group of animals to which the specimen may belong. Dr. Carpen- 

 ter has in his " Manual " given measurements of examples taken 

 from each group of the vertebrata. 



Under from 400 to 600 diameters a cell, with clear contents, 

 and a nucleus, is seen exactly filling the lacunse, and sometimes 

 even nmning up the canaliculi for a short distance. 



All bone we know to be either ossified cartilage or membrane, 

 the nucleus of the lacunje is the nucleus of the previously existing 

 cartilage cell. As membrane has no definite structure like cartilage, 

 I once thought that a microscopic distinction might be detected in 

 the completely- formed bone ; but, after several experiments, I could 

 find none, and Kolliker states that there is none, and that pre- 

 viously to ossification taking place in a membrane, plasma cells 

 are produced, the nuclei of which form the nuclei of the lacunae. 

 Kolliker also states that the cells of the lacunae may be detached as 

 separate stellate cells by treating a section with dilute hydrochloric 

 acid, and then for a moment boiling in dilute caustic potash. 

 I have tried this, but failed ; nor have I yet been able to detect 

 the ultimate osseous granules of bone mentioned and figured in the 

 article on bone in the " English Cyclopaedia." 



With respect to the preparation of bone for Microscopic examin- 

 ation, the operation is not difficult. Thin sections, well polished 

 and mounted dry, are usually considered best, but I prefer that 

 method described by Dr. Carpenter in his " Manual," page 702, in 

 which thick Canada balsam is used. If this method be properly 

 carried out, the lacunae and canaliculi come out beautifully defined, 

 even those of the deep-seated cells. The drawback is that the 

 balsam may run in and obliterate some of the cells situate at the 

 edge of the specimen. But if injury should thus happen to a 

 section, chloroform will speedily restore it to its original condition. 



