f04 APPENDIX. 



If the balsam has the proper consistence, about that of syrup, the slide is 

 held for a few moments over a spirit flame, the slight heating facilitating the 

 distribution of the balsam over the section. The cover-glass, previously 

 scrupulously cleaned and in readiness, is grasped between the clean blades 

 of the forceps, held for a moment over the spirit flame, and gently lowered 

 on the slide in such manner that the left edge of the cover is brought first into 

 contact with the balsam. As soon as this contact is made, a moment's pause 

 is advantageous to allow the balsam to spread out beneath the cover, which 

 is then steadily and slowly lowered into position over the specimen until the 

 entire space between the slide and cover is filled with the mounting medium. 

 If, after very gentle pressure on the cover-glass with a clean needle, part of 

 this space remains unfilled, additional balsam must be run in until the space 

 is completely occupied by the mounting medium. Care must be exer- 

 cised lest any excess of balsam get on the surface of the cover ; otherwise 

 it does not interfere with the immediate examination of the preparation. 

 A slight edging of balsam around the cover is useful, since it dries 

 much sooner than the medium beneath the cover and thereby adds 

 materially to the fixation of the latter. While avoiding as far as possible 

 the imprisonment of air-bubbles, should these be present after the cover is 

 in place, they need cause no concern, as they usually spontaneously 

 disappear during the next twelve hours, unless enclosed within some recess 

 or fold in the section. 



While the preparation may be examined under the microscope as soon 

 as properly mounted, care being taken to keep it horizontal to avoid possible 

 slipping of the cover-glass, no attempt should be made to finish it until the 

 balsam around the edges of the cover has sufficiently hardened to preclude 

 displacement. Ordinarily this requires some weeks, but the process of hard- 

 ening may be facilitated greatly by subjecting the freshly mounted specimen, 

 in some suitable place protected from dust, to continuous gentle heat. After 

 a few days of such drying, although the balsam in the centre of the prepara- 

 tion may remain fluid, the cover will be so securely fixed that the specimen 

 may be finished and labelled. If the superfluous balsam be considerable, as 

 much as possible should be removed by the knife, care being taken not to 

 touch the cover-glass, and the slide finally cleaned with a cloth moistened 

 with xylol. Disturbing the cover-glass will likely ruin the preparation and, 

 hence, this danger is to be constantly borne in mind. 



After the slide has been cleaned, not forgetting the under side, labels 

 are attached at the ends. Data of importance, regarding tissue, source, 

 method of fixation, staining, and date, should be noted on one label and never 

 be entrusted to memory; failure to observe such precautions is often a con- 

 stant source of uncertainty and regret in later years. When preparations 

 include serial sections, numbers or letters on the labels should indicate the 

 sequence of the slides. Much time may be saved by marking the slides as 

 to order with a writing diamond before they receive the sections. The 

 second label is convenient for memoranda concerning special features shown 

 by the preparation. Where many specimens accumulate, some system of 

 card-catalogue well repays in convenience for future reference. The various 

 methods of storing microscopical preparations are matters of individual 

 preference and expediency, provided two essentials are observed that the 

 slides lie horizontal and are protected from light. With proper precautions 

 against the presence of acid in the sections, even hematoxylin preparations 

 may be preserved for many years without deterioration. 



