1881.] 



MICROSCOPICAL JOURNAL. 



143 



shown in Fig. 28. This method of 

 keeping cover-glasses not only pre- 

 serves them from breakage, and en- 



FiG. 38. 



ables one to readily pick them out 

 when wanted for use, but also enables 

 one to select for special preparations 

 those of the most desirable thickness. 

 For, by holding the drawer or box 

 between the eye and the source of 

 light, it is easy, by comparison, to 

 select the thickest or thinnest cover, 

 and thus, for all practical purposes, 

 to do away with the trouble of meas- 

 uring them. 



And now a few words on the sub- 

 ject of a quick and simple method of 

 centering mounts, and of cementing 

 the cover-glass. Every one will ad- 

 mit that a neatly mounted prepara- 

 tion, perfectly centered on the slide, is 

 preferable to one mounted in a slov- 

 enly manner. Many students, how- 

 ever, feel that time is too precious to 

 waste in what seems unnecessary la- 

 bor, so long as the preparation is 

 good, and shows the structure to best 

 advantage. While I admit that the 

 beautiful and instructive preparations 

 of some of the greatest histologists 

 are often rudely mounted, I insist 

 that this untidy appearance is no 

 merit, and that the preservation of 

 the object would be made much more 

 certain if a little more attention 

 were given to the cementing of the 

 cover-glass. The use of circular 

 covers and a self-centering turn-table 

 renders it possible to make the wall 

 of cement around the edge of the 

 cover much more perfect than can 

 possibly be done in any other way. 



The hints to be given here are to 

 enable the student to save time in 

 this kind of work, and yet produce 

 results equal to the slower and more 

 tedious methods usually employed. 



First, let me say a word about 

 cements. In an experience of more 

 than twelve years, during which I 

 have used nearly every kind of cement 

 that has been suggested in the jour- 

 nals and books, published in England 

 and America, I have arrived at the 

 conclusion that two, or at most three, 

 cements are capable of insuring the 

 preservation of an object in any 

 medium the microscopist will find it 

 necessary to employ. These are 

 gold-size (Windsor & Newton's), the 

 ordinary dammar mounting medium, 

 and possibly, for occasional use, the 

 dammar medium to which a small 

 proportion of a solution of rubber in 

 naphtha has been added. Dr. Seiler 

 and others have directed the student 

 to apply his cements in several coats, 

 using great care in holding the brush, 

 and as to the quantity of cement in the 

 brush. I have for several years saved 

 myself much of the time required 

 by such methods of manipulation, 

 by putting on the cement in a broad 

 band over the junction of the cover 

 with the slide, and then, spinning the 

 turn-table as rapidly as possible, run- 

 ning the cement into a narrow band, 

 in its proper place, by holding a 

 knife-blade first on the slide and 

 then on the cover, in such a manner 

 as to cause the cement, spread out by 

 the brush, to heap itself up into a 

 narrow but perfect ring. One coat- 

 ing of cement thus put on is equal to 

 three or four coats by the other 

 method, while the polish of the ring 

 far surpasses in perfection the brush- 

 made ring. If it is desired to color 

 the ring, instead of using anilin 

 mixed with the cement, I recommend 

 the use of the more transparent of the 

 water-colors, such as the student will 

 need to have by him for the purpose 

 of coloring his drawings. The man- 

 ner of their application is this : after 

 the dried balsam or dammar has been 



