SKCTIONS OF CEREBRAL AND CEREBELLAR CORTEX. 73 



staining may now be removed, by keeping them in a vessel 

 containing methylated spirit for some hours. When suffi- 

 ciently washed by this measure, as may be seen immediately 

 by the removal of a section to the stage of the microscope, 

 and examining it with a low power, the tint of the ger- 

 minal centres dyed in this way may be darkened by exposure 

 of the slide for a few seconds to the vapour of ammonia, or 

 to a faintly alkaline spirit. They are next cleared in the 

 usual way with oil of cloves, and mounted in balsam. 



The Aniline series of Dyes. — Magenta or rosaniline is a 

 powerful and active dye, but its solubility in spirit is so 

 great that its eflfects are not permanent, and the difficulties in 

 fixing this reagent have proved insuperable obstacles in the 

 way of its employment for these purposes. Judson's purple 

 dye also shares in this disadvantage, but to a less extent. 

 The latter may be used in producing the peculiar conditions 

 of refractive power in the tissue elements which are described 

 under the heading of carmine ; but for these results the 

 picro-carmine solution far surpasses any of the aniline or 

 Judson's series of dyes. To Mr. W. H. O. Sanky belongs 

 the credit of introducing to our notice the aniline black as 

 a staining reagent applicable to the microscopic investigation 

 of cerebral tissues. A section of human cerebellum exhibited 

 by him at the last annual conversazione, held at the West 

 Riding Asylum, attracted great and deserved attention. The 

 cells of Purkinje and their processes were shown with extra- 

 ordinary beauty. His process has been described in the 

 pages of the * Lancet ; ' but for full details I would refer my 

 reader to the ' West Riding Asylum Reports ' for this year, 

 where an extremely interesting paper by Mr. Sanky will be 

 found, together with most faithful and beautiful plates of 

 the cerebellar cortex, &c. The process he adopts for drying 

 fresh brain for sections I have not tried, but the aniline 

 black as a dye I have used extensively and with the best 

 results. My experience leads me to recommend two distinct 

 methods as productive of most satisfactory slides. The solu- 

 tions of aniline black employed by me are three, varying in 

 strength as follows : 0"25, 0*5 and 1 per cent. It may be 

 dissolved in water, alcohol, or even glycerine ; but for most 

 purposes the aqueous solution is the most useful. It is a 

 matter of no difficulty with this reagent to dye to any depth, 

 but the M^ashing-out of diiffuse staining is at first rather per- 

 plexing. The solvents of aniline which present themselves 

 as useful accessories here are absolute alcohol, methylated 

 or rectified spirit, glycerine, or glycerine and water. These, 

 however, do not not succeed with me in demonstrating satis- 



