BONE, TEETH 431 



6. Place in the following solution for twenty-four hours : — 



Hydroquinone . . . . 1 to 1-5 grm. 



Distilled water .... 100 c.c. 



Formol . . . . . 5 to 10 c.c. 



Rectified spirit . . . . 10 to 15 c.c. 



7. Wash in water for some minutes. 



8. Cut sections, and mount. 



The presence of nerve-end cells in the dental pulp was demon- 

 strated by Mummery {Phil. Trans. B., ccix, 1920), by means of 

 a modification of the gold method of Beckwith. 



Teeth, immediately after extraction, are placed in a solution 

 of formol and water or of formol and normal salt solution, pre- 

 ferably 4 per cent, of formol. This is, after a few days, changed 

 to a 10 per cent, solution, and the teeth kept in this for at least a 

 fortnight. 



Decalcification is effected by means of a 33-3 per cent, solution 

 of formic acid in distilled water, to which 5 per cent, of formol 

 may be added. (Mummery states that neither he nor Dependorf 

 has ever procured good nerve preparations of teeth which have 

 been decalcified in the mineral acids.) 



Wash in running water for twenty-four hours, then for a few 

 minutes in distilled water. 



The pieces are taken from the distilled water and suspended 

 by threads in a large quantity of a weak solution of gold chloride 

 (1 in 5000). Each piece should be suspended in at least 100 c.c. 

 of the solution, in which it is left in the dark for from four days 

 to one w^eek, according to its size. On removal from the gold 

 solution it is washed for a few minutes only in distilled water. 

 Reduction is effected by placing the pieces in a 20 per cent, 

 solution of caustic soda for four minutes, then rinsing in water 

 and placing in a 10 per cent, solution of potassium carbonate 

 for from half an hour to an hour. This is then drained off, and 

 the pieces are placed in a 10 per cent, solution of potassium 

 iodide for a short time — -usually five to ten minutes. As soon 

 as seen to darken, the pieces are removed from this solution to 

 water, placed in gum for twelve hours, and sections cut on the 

 freezing microtome. 



After dehydration the sections are mounted in camsal (propylic) 

 balsam. 



917. ViVANTE {Intern. Monalsschr. Anat. u. Phys., ix, 1892, p. 398) 

 impregnates portions of frontal bone of four to six months' calves, which 

 are not more than 3 to 4 millimetres thick, by Golgi's rapid bichromate 

 and silver process. After impregnation the specimens should be 

 decalcified in von Ebner's mixture (§ 913), well washed with water, and 

 brought into solution of carbonate of soda, and finally imbedded in 

 paraffin. For his quinolein blue method see fourth edition. 



For Underwood's gold process for teeth, and for that of Lepkowski, 

 see third edition, or Anat. Anz., 1892, p. 294. 



