APPENDIX. 423 



cause no concern, as they usually spontaneously disappear during the 

 next twelve hours unless imprisoned within some enclosed recess 

 of the tissue ; rough treatment, by strongly and repeatedly pressing 

 on the cover-glass in the attempt to displace air-bubbles, is disastrous 

 to thin sections, and should never be practised ; gentle pressure, 

 however, should be made after the cover is down, to press out super- 

 fluous balsam, but this must be done with care and judgment. The 

 balsam should entirely fill up the space beneath the cover and form 

 a slight border outside ; this edging of balsam is useful, as it dries 

 much sooner than the medium beneath the cover and adds very 

 materially to the strength of the preparation. 



The freshly-mounted slides should be placed in the horizontal 

 position and allowed to dry some days before being much handled, 

 although if necessary a preliminary study of them can be made at 

 once. No attempt should be made to clean them until the balsam 

 has well hardened and all danger of moving the cover-glass disap- 

 peared ; the excess of the mounting medium is then removed with 

 a sharp knife and the slide finally cleaned by a cloth moistened with 

 benzole. 



8. Finishing, labelling, and storing the slides depend largely 

 upon the individual taste and wishes of the worker ; while the earnest 

 investigator has little time for useless ornamentation, the small amount 

 of labor involved in having slides clean, neat, and properly labelled 

 is well compensated by the convenience and satisfaction of handling 

 such preparations. Labels should always be attached as soon as 

 practicable, and should indicate all data likely to be of interest ; 

 when labels are placed on both ends of the slide, one should be re- 

 served for noting points of especial interest shown by the preparation. 

 In preparing slides on which an entire series is mounted, marking 

 each with a diamond saves much vexatious delay, which otherwise is 

 often experienced in determining the proper sequence. Finished 

 preparations are best preserved in some form of cabinet or case, the 

 exact character of which is of little consequence so long as the slides 

 are protected from dust and light and lie flat ; cabinets with well-made 

 drawers are attractive and convenient, but usually expensive. 



In recapitulation of the foregoing manipulations, already considered 

 in detail, the steps necessary to convert the fresh tissue into the 

 finished preparation may be presented as 



AN OUTLINE OF THE STANDARD METHOD. 



1. Fixation of fresh tissue in large quantity of Muller's fluid ; 

 renewal when turbid ; tissue remains 2-3 weeks. 



2. Thorough washing in running water 2-5 hours. 



