490 APPENDIX. 



crometer ruled into squares answers most purposes and 

 the squares and objects delineated should be drawn to 

 the proportions observed. Having thus a record of ob- 

 jects, drawn in proportion relative to the said squares, 

 it remains but to ascertain the value of the latter. This 

 is best done by using, in conjunction with the eye-piece 

 micrometer above named, a stage micrometer ruled to 

 intervals of known value ; there will thus be superposed 

 lines of absolute and relative measurement. The actual 

 value of the squares of the eye-piece micrometer may by 

 this means be once for all calculated, and a record of the 

 same should be kept for each lens combination. 



E. PREPARATION AND USE OF REAGENTS 

 AND CULTURE SOLUTIONS. 



The reagents employed in microscope work are best put up 

 for use in J oz. bottles. Those marked thus * should be kept in 

 glass bottles with ground necks and stoppers, their contents 

 being removed by means of clean capillary tubes. The re- 

 ceptacles of the remaining ones should be corked, each cork to 

 carry a thin glass rod long enough to reach near the bottom of 

 the bottle. 



i. Acetic acid, Dilute. 



Mix i cub. centimetre of glacial acetic acid with 99 cub. 

 cent, of distilled water. 



2. Alcohol. 



Methylated spirit should be kept ready to hand in stock 

 bottles, diluted with water to various strengths, viz. — 

 50 per cent., 75 per cent., 90 per cent. Upon placing 

 any specimen, organ, or tissue in the same, at least 3 — 4 

 times its bulk in fluid should be employed. Immersion 

 in the weaker solutions should not exceed 6 — 8 hours in 

 the case of whole organs, or 2 — 3 hours in those of 

 tissues in course of hardening for histological work. 



