The Microscope. 137 



be found that if the hands are entirely free from any greasy material 

 and are perhaps a trifle moist from perspiration or from being 

 breathed upon that by this method the sections will flatten out per- 

 fectly and will not adhere to the finger. If the sections do adhere 

 to the finger, it indicates that the hand is not perfectly clean and 

 should be washed with hot water and soap, and oftentimes with 

 alcohol, for when the soap does not sufficiently remove the greasy 

 material upon the fingers, alcohol will do so efficiently and quickly ; 

 in my laboratory, I am accustomed to washing the fingers with the 

 old alcohol which has been laid aside for redistillation. 



The slide with the rolled section upon it is dipped in perfectly 

 clean alcohol of 96*"' and held there until the paraffine is thoroughly 

 wetted, this can be seen by the changes of color; the slide is withdrawn 

 from the alcohol and held in a vertical position so that the alcohol 

 may drain off, after which the slide is then placed upright to dry ; after 

 drying the sections are covered by a second coat of celloidine, and 

 when that is dry, the slide is warmed over a lamp very carefully just 

 enough to entirely melt the paraffine ; the slide is allowed to cool 

 and the paraffine may now be dissolved out with turpentine and the 

 sections are ready to mount. 



For mounting it is indispensable to use exceedingly thin balsam. 

 I recommend pure Canada balsam diluted with a large quantity of 

 pure benzole. It is at this point that the inexperienced usually 

 meet with their mishaps, for it is very hard to induce those accus- 

 tomed to the ordinai-y methods of mounting to use balsam in suffi- 

 cient quantity and sufficiently thinned out with benzole. 



If the directions are followed the sections will keep their places 

 perfectly ; if they are not followed some of the sections are pretty 

 sure to get torn or broken. This method of mounting I consider 

 satisfactory except in one respect, that now and then there are little 

 bubbles under the sections, the origin of which I do not quite under- 

 stand and which interfere with the sections lying perfectly flat. 

 But when the mounting is carefully done, most of these bubbles 

 disappear in course of the manipulation, and for some unaccount- 

 able reason, the more familiar one becomes with the processes 

 employed the more the bubbles stay away. If it was not for this one 

 defect I should recommend the method quite unreservedly ; it is 

 essentially that which I learned from by friend Dr. Drasch of the 

 Physiological Institute at Leipsic. It can also be employed when 

 it is desired to stain the sections on the slide; for this purpose, the 

 slide, after the paraffine has been dissolved by turpentine, is washed 



