310 SUMMARY OF CURRENT RESEARCHES RELATING TO 



detached with a slight pressure. The surface of the glass having 

 the diatoms is then blown and brushed, and the preparation is 

 completed by the process described for arranging diatoms. 



The essential point of the operation is in sufficiently hardening 

 the balsam on the cover-glass. The heating must be carried as far 

 as is possible without altering the colour. To succeed, it is advisable 

 to cover the spirit-lamp with a metal chimney to avoid the flickering 

 of the flame. This chimney has a cap (g, fig. 42, C and D), movable 

 vertically, so that it can be raised or lowered. It is also convenient 

 to joint it in such a manner that the hot plate can be placed perpen- 

 dicularly, if desired. 



It is, of course, permissible to increase at pleasure the number of 

 tubes. The author makes preparations containing sixteen and even 

 twenty-five varieties of earths ; and expects to greatly exceed this 

 number. Indeed, the only limit is the size of the cover-glass. 



Logwood Staining.* — A. C. Cole says that "up to the present 

 time, no stain has been found to equal logwood for certainty and per- 

 manency of results, and beauty of colour, which, besides being 

 beautiful, is also not too tiring for the eye. We go further, and say 

 that the more a histologist departs from a use of logwood and adopts 

 other stains, the more unsatisfactory will be his total results. If ten 

 men were each to make for himself a histological cabinet, the work of 

 each being equal in other ways, the one who would produce the best 

 cabinet would be found to have used logwood and picro-carminate of 

 ammonia for the great majority of his slides, using other stains which 

 have been found to suit special cases, such as aniline-blue-black for 

 nerve-centres, methyl-aniline for amyloid or waxy degenerations in 

 pathological histology in a few cases only. He would further have 

 been found to have used benzole balsam as his mounting medium in 

 the case of his logwood stains, and glycerine jelly for mounting his 

 picro-carmine slides. Such a cabinet would last a thousand years, 

 and be as perfect the last day as on the first. On the other hand, 

 the worst cabinet, especially after, say about ten years, would be 

 found to have been composed of a few logwood slides, mounted in 

 dammar varnish, and the great majority stained with all sorts of 

 aniline and other fancy dyes, and mounted in glycerine. The 

 dammar preparations would be found to be little better than fine 

 grey dust, and the fancy dyes to be conspicuous by their absence. 

 So far as can be judged by our present data, a preparation stained 

 with logwood and mounted in balsam is unchangeable ; so is a pre- 

 paration stained with picro-carminate of ammonia and mounted in 

 good glycerine jelly. 



With these preliminary remarks, we now proceed to give formulsB 

 for those stains, and those only, which have been found really good in 

 every way. As staining is yet in its infancy, we daily read of a fresh 

 stain, and a new method of staining. We need scarcely draw the 

 attention of our readers to the present mania for ' rushing into print,' 

 and the numerous worthless, not to say senseless, communications to 



* ' The Methods of Microscopical Eesearch,' Part VII. (1884) p, xli. 



