72 W. BEVAN LEWIS. 



of the section. Now this appearance may be fixed hy sud- 

 denly dropping over its surface a little balsam and perma- 

 nently mounting. Upon this fact depends the process now 

 to be described. Sections treated by Beale's carmine solution 

 (1 to 7 in strength) and washed with the acid wash are 

 placed, saturated 'v\'ith spirit, upon a slide. When the spirit 

 has nearly all evaporated a drop of oil of anise is allowed to 

 flow over the section (not to float it up), and the clearing 

 process is watched on the stage of the microscope ; then, 

 just when the appearance referred to above is presented to 

 view, a drop of balsam is allowed to run over the section and 

 a covering glass permanently fixed on. In lieu of the oil of 

 anise I frequently employed glycerine with the same results, 

 and mount ultimately in glycerine jelly. Still better eff'ects 

 may be obtained by the following method. 



Picro-carmine Staining. — I use the solution recommended 

 by E-anvier, the sections being left in it for an hour. I then 

 transfer them to a strong ammoniacal solution of carmine 

 for the space of twenty minutes, and on removal wash freely 

 and mount, as in the process described above. The appear- 

 ance of sections of cerebellum treated thus is very striking, 

 and the cells of Purkinje and their processes are far better 

 delineated than by the usual carmine method. 



Logwood Staining. — Formulae for the cannine dyes are well 

 known ; not so, however, those for hsematoxylin. Bohmer, 

 who first employed logwood for these purposes, gives a 

 formula which is quoted by Frey.^ I may also refer the 

 reader for an excellent foi^mula for the logwood solution to 

 the pages of ' The Lens ' for July, 1872. The solution 

 usually sold under this name varies greatly in efliciency, and 

 I am told by one of the most eminent authorities in cere- 

 bral histology that this variability has proved a matter of 

 great and constant annoyance to him. 1 must confess to a 

 similar experience in my employment of this reagent. When, 

 however, the proper solution can be obtained, it undoubtedly 

 stands in the foremost ranks of staining fluids, its results 

 being unrivalled for the major details in the cerebral cortex. 

 Of the solution sold as logwood dye about ten drops should 

 be added to each drachm of distilled water, carefully filtered 

 and exposed for a short period to the air. The sections 

 should remain in it until the required depth of colour is ob- 

 tained, the logwood poured off", and the pieces well washed 

 by allowing a stream of water to flow on to the inclined side 

 of the porcelain vessels in which they are held. All diffuse 



1 ' The Microscope and Microscopic Technology,' translated by Cutten, 

 page 158. 



