422 SOME OTHER HISTOLOGICAL METHODS. 



between two plates of old ground glass, with water and 

 pumice powder, and mounted, surface dry, in stiff balsam or 

 sty rax, care being taken to use as little heat as possible. 

 Lacunas, canaliculi, and dentinal tubuli are found infiltrated 

 by the coloured collodion. 



MATSCHTNSKY (Arch.f. mik. Anat., xxxix, 1892, p. 151 ; Zeit. 

 f. wiss. Mik., ix, 3, 1893, p. 353) prepares sections by soaking 

 in gum and rubbing down as recommended by B-anvier. 

 When sufficiently thin, the gum is removed by means of water, 

 the sections dried, put for half an hour into benzin or ether, 

 and stained in a saturated aqueous solution of some anilin 

 dye, from one to seven days according to the age of the bone. 

 They are then washed in water, further ground down, put for 

 twenty-four hours into alcohol, and mounted by the aid of 

 heat in thickened balsam. The ^result is a stain of the ground 

 substance, of varying degrees of intensity. 



HOPEWELL-SMITH (Journ. Brit. Dent. Ass., xi, 1890, p. 310 ; 

 Journ. Roy. Mic. Soc., 1890, p. 529) says that for preparing 

 sections of teeth showing odontoblasts in situ the best plan is 

 to take embryonic tissues. A lower jaw of an embryonic 

 kitten or pup may be taken, and hardened in solution of 

 Miiller followed by alcohol, then cut with a freezing micro- 

 tome. The knife cuts quite easily the thin cap of semi- calcified 

 dentine and bone. 



797, Bone and Teeth, Decalcification Methods. Besides the 

 processes given in Chap. XXIV, attention may be called to 

 the following : 



HOPEWELL-SMITH (Trans. Odont. Soc., xxiv, 1891, p. 20; 

 Journ. Roy. Mic. Soc., 1892, p. 433). Harden a newly-ex- 

 tracted tooth in solution of Miiller (three to four weeks) 

 followed by alcohol. Wash in water, and seal up apical fora- 

 men with collodion. Decalcify as directed in 565. Wash 

 with distilled water. Divide with a razor into several pieces, 

 wash them in water, and put them for twelve to fifteen hours 

 into gum mucilage (B.P.). Cut with a freezing microtome, and 

 stain with orange-rubin, gold-chloride, borax-carmine, or by 

 Weigert's method. Dehydrate, clear with cedar oil, and 

 mount in balsam. 



798. LKPKOWSKY ( Anat. Anz., vii, 1892, p. 274; Zeit. f. wiss. 

 Mik., ix, 3, 1893, p. 355) recommends the following as giving 



