20 MICROSCOPY. 



or by placing the finger nail beneath the section, the student can de- 

 termine whether the process is complete. The reagents commonly 

 used for clearing purposes are creosote, cedar oil, xylol, benzole, 

 clove oil, and aniline oil. 



10. Mounting consists in permanently attaching the cover- 

 glass for the protection of the specimen. Balsam and glycerine- 

 jelly are generally used for this purpose. For laboratory work the 

 balsam method will be found the most convenient. Place upon the 

 cover-glass, while holding it between the fingers, a drop of balsam, 

 and then (balsam down) let it fall gently upon the section. After 

 centering the cover-glass, apply gentle pressure by means of a dis- 

 secting needle, so as to force the balsam out to the edges of the glass. 

 Should too much balsam be used, it may be removed (when thor- 

 oughly dried) with a pen-knife. This method will be found more 

 satisfactory than to undertake its removal with cloth or brush by 

 means of xylol. The safest plan is to use just enough balsam, no 

 more, no less. 



11, Labeling. Two labels should be used, one on each end of the 

 slide, and they should be so applied that the edges of the labels will 

 be the same distance from the edges of the slide. The left hand label 

 should indicate the number of the preparation, the staining fluid, 

 the mounting medium, the date, and the name of the student. The 

 right hand label should indicate the kind of tissue, the character of 

 the section (whether transverse, longitudinal, vertical, or oblique), 

 the condition of the specimen (whether normal or abnormal), and 

 the animal from which it has been obtained. After labeling, the 

 preparation should be placed in the slide-box in a horizontal posi- 

 tion, with the cover-glass up, and kept in that position until the bal- 

 sam hardens. 



II. SPECIAL TREATMENT OF TISSUES AND ORGANS. 



The structures required for microscopic work may be obtained 

 from some animal, such as the cat, rabbit, or guinea pig. Should a 

 cat be used, it may be killed by placing it under an inverted bowl 

 (resting upon a heavy sheet of paper upon a table or floor), and then 

 inserting a sponge saturated with chloroform. In twenty minutes 

 the animal will be dead and ready for injection. 



Injecting. To inject the animal, the following process may be 



