The Michoscope. D'J 



■without at the same time breaking or moving the cover, ghiss or 

 otherwise injuring the mount. 



It seems to be worth while to emphasize a fact that is over- 

 looked in the books, where the cleaning away of balsam is made to 

 appear as an unavoidable accompaniment of mounting in that 

 medium. The truth is that there should be no surplus balsam 

 whatever, as it is an unnecessary evil, due to miscalculation on the 

 part of the preparer. 



From experience, I find it is not difficult to graduate the 

 amount of balsam used so that it will fill the space required without 

 exuding. The balsam should be placed in the center of the slide, 

 and the cover should be placed over it, so that the balsam is in its 

 center. A very slight heat will make the balsam flow, if not already 

 liquid enough, so that it will extend to the edge of the cover all 

 around, and thus exactly fill the space and no more. If an object 

 is to be mounted that requires pressure by the cover to keep it flat 

 till the balsam is hard, of course only a very small amount of balsam 

 is needed. In fact it is a good rule in all cases to use a little less 

 balsam than seems neeessaiy, as by a little pressure on the cover the 

 balsam can be squeezed out to the edge. 



Of course, these remarks apply only to the use of balsam with- 

 out a regular cell, and this method is quickest, and answers admir- 

 ably in almost all cases, unless a very thick object is to be mounted. 

 AVhen a cell is used it is impossible to avoid a small excess of balsam, 

 as it needs to exude slightly around the cover to drive out the air 

 fi'om the cell, but even in this case if carefully graduated to the cell 

 the excess need not be noticeable, and it can be covered with a ring 

 of cement without being cleaned away at all. 



Many microscopes are packed away and uo work is done with 

 them, for the reason that the owner met with such discouraging 

 obstacles in his attempts at balsam mounting. For this reason it 

 seems desirable that such of the TTSual difficulties of mounting in that 

 substance as are avoidable, should be pointed out and emphasized. 



MORE ABOUT CELLOIDINE. 



WILLIAM BUCKINGHAM CANFIELD, A. M., M. D. 

 Lecturer on Normal Histology in the University of Maryland, Baltimore. 



^VTOTWITHSTANDINO the frequent contributions on the sub- 

 -^ ^ ject of celloidine as an embedding agent, a few words here may 

 not be out of place. Although celloidine can be used for every kind 

 of embedding, certain sections are much better made in paraffin, and 

 particularly sections of small organs (whether previously stained in 



