CHAPTER XXIX. 371 



HANAZAWA (Dental Cosmos, lix, 1917, pp. 125 et seq,) gives a number 

 of methods for staining ground and decalcified sections of dentine to 

 demonstrate its minute structure. 



MATSCHINSKY (Arch. mile. Anat., xxxix, 1892, p. 151, and xlvi, 1895, 

 p. 290), after grinding, impregnates with nitrate of silver. 



For similar method of RUPRECHT, see Zeit. wiss. Mile., xiii, 1896, p. 21, 

 wherein see also quoted (p. 23) a method of ZIMMERMANN. 



CSOKOR (Verh. (mat. Ges.,1892, p. 270) dascribes a saw which will cut 

 fresh bone to 120 p. and ARNDT (Zeit. wiss. Mik., xviii, 1901, p. 146) a 

 double saw which will also give very thin sections. 



774. Mounting. To show lacunae and canaliculi injected with 

 air, take a section, or piece of very thin flat bone, quite dry. Place 

 on a slide a small lump of solid balsam, and apply just enough heat 

 to melt it. Do the same with a cover glass, place the bone in the 

 balsam, cover, and cool rapidly. 



When thin ground sections of enamel are mounted in Canada 

 balsam it is found often that they appear almost structureless. 

 To demonstrate the enamel pattern of such sections they may be 

 etched by immersion in -6 per cent, of hydrochloric acid in 70 per 

 cent, alcohol, or in a weak aqueous solution of picric acid, and 

 mounted in Camsal balsam or Euparal, media which, on account of 

 their low index of refraction, will be found to disclose the structure 

 of the enamel more easily. 



775. Sections of Bones or Teeth showing the Soft Parts. A 



developing tooth with its epithelial enamel-organ, its mesodermal 

 dentinal papilla, and its layers of partially calcified enamel and den- 

 tine, is made up of very delicate structures of different consistency 

 and so peculiarly liable to unequal shrinkage, with consequent 

 distortion during the period of fixation and in the subsequent 

 processes passed through in the preparation of sections. Further, 

 post-mortem changes in the ameloblasts occur within a very few 

 minutes after death leading to a less precise behaviour to stains than 

 is found in the case of cells which are fixed immediately after death. 



For the examination of developing teeth in situ, jaws may be 

 fixed in corrosive-formalin-acetic mixture, in Bouin's picro-formol, 

 in Zenker's mixture or Helly's modification thereof, or in Sansom's 

 modification of Carnoy's mixture ( 86). 



For the study of the micro-anatomy of the enamel-organ and the 

 dentinal papilla, a young pup or a kitten, two or three days old, 

 is killed, preferably by a blow on the head. The jaws are removed 

 and the bone of the under-surface of the mandible pared away by a 



sharp scalpel until the bases of the tooth-germs are almost exposed. 



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