1894.] MICROSCOPICAL JOURNAL. 279 



time they will become intensely colored. The excess of 

 dye is removed by placing the sections in 70 per cent, 

 alcohol, to which 1 gramme of hydrochloric acid has been 

 added to each 100 C.cm. for as long as they have been in 

 the dye. It is then well to place them in 90 per cent. 

 alcohol for about twelve hours, and afterwards in oil of 

 cloves for one or two hours. This last procedure makes 

 the specimens more transparent. 



We have now come to the treatment with Canada bal- 

 sam. This must in the meantime have been prepared in 

 the following manner : A quantity of Canada balsam, 

 as obtained from the druggist, is placed in an evaporat- 

 ing dish, and kept over boiling water until the balsam, 

 by cooling, becomes solid and brittle like glass. This 

 takes from twenty to thirty hours, according to the qual- 

 ity of the balsam. 



When the sections are taken from the oil, they must 

 be cleaned with pure xylol, and then quickly immersed 

 in chloroform, to remain twenty-four hours. Then suf- 

 ficient of the hardened Canada balsam is added to the 

 chloroform to give a weak solution, and after another 

 twenty-four hours the solution must be saturated with 

 Canada balsam ; but the solution containing the speci- 

 mens is then again put into an evaporating dish, and 

 placed over hot water until the balsam once more be- 

 comes solid. As the chloroform boils at "a low tempera- 

 ture (60-61° C), the heat from the water must, to begin 

 with, not be higher than about 60° C. ; later it can be 

 increased, but altogether slowness of the solidifying pro- 

 cess is in favor of the results. Consequently, the proce- 

 dure takes from twenty to thirty hours. 



When the balsam, by cooling, becomes solid and brit- 

 tle, the specimens can be cut out with a small, sharp 

 chisel, and with a fine, sharp scroll-saw be cut into sec- 

 tions suitable for grinding. The grinding is done as 

 wl^en small sections of bone are ground for microscopic 



