372 APPENDIX 



tilled water, allow the solution to cool and add it to the 

 above solution. 



5. Dilute to one liter with distilled water. 



6. Allow to stand for one week and decant for use. 



MOUNTING MEDIA 



Canada balsam for making permanent mounts of mi- 

 croscopic preparations : 



Canada balsam, dry, hard, for microscopic use 4 parts 



Xylol 3 parts 



This gives a mounting medium of about the right con- 

 sistency. It should not " thread " when a drop is taken 

 out with the glass rod. Balsam should be kept in a bottle 

 stoppered with a glass bell-stopper, and having a rim 

 arranged so that the excess of balsam taken upon the 

 glass rod can be drained off. 



Immersion oil for oil immersion objectives. 



It is necessary that the immersion oil have practically 

 the same index of refraction as glass in order to avoid 

 dispersion of any of the light rays. Cedar wood oil having 

 a refractive index of 1.515 to 1.520 is the usual medium 

 interposed between the specimen and the oil immersion 

 objective as it has approximately the same index of refrac- 

 tion as crown glass, 1.518. The refractive index of air is 

 1.000. 



Chinese ink: 



Bum's " Pelikan " Chinese ink 1 part. 



Distilled water 7 parts. 



Tube, using 8 to 10 c.c. per tube, sterilize in the autoclav 

 and allow to stand two or three weeks without disturbing, 

 for sedimentation to take place. It is to be used without 

 shaking or disturbing any more than necessary. 



