SECTIONS OF CEREBRAL AND CEREBELLAR CORTEX. 75 



employ oil of anise and oil of cloves indiscriminately, both 

 being of high refractive powers. The former has, however, 

 the disadvantage of solidifying at ordinary temperatures. 

 Its oxidized compound stearoptene, which forms the greater 

 bulk of the oil, and which separates in a solid mass, may, 

 however, by a very gentle warmth be kept in a fluid state 

 during the process. The beautiful eifects of logwood stain- 

 ing may also be obtained for the granular layer, Avhilst the 

 layer of Purkinje's cells and their antler like processes may 

 be produced with all the accurate details of aniline-staining 

 by a process which I now proceed to describe. 



Double Staining loitli Logwood and Aniline. — It will soon 

 be noticed by those who attempt a logwood staining of the 

 cerebellar cortex, that whilst the granular layer nuclei of 

 blood-vessels and nerve-fibres are beautifully stained, the 

 cells of Purkinje and their processes remain very faintly or 

 not at all affected by the colouring reagent ; the aniline 

 black, on the other hand, appears to possess special affinities 

 for these latter structures. If, therefore, sections dyed with 

 logwood are immersed for a few seconds only in a solution of 

 aniline black of a strength of 0*25 to 0*5 per cent., it will 

 be found that the logwood staining still remains, whilst the 

 layer of Purkinje has taken up the aniline sufficiently to 

 afford a decided and beautiful contrast. The chloral hydrate 

 should now be used, but the alcoholic solution is not here 

 advisable. They should be well washed from the chloral 

 with a stream of water, rapidly dehydrated by alcohol, 

 cleared with oil of cloves, and mounted in balsam. 



Summary. — Having so far dwelt on the more general 

 methods employed for demonstrating the structure of the 

 cineritious substance of the brain, I shall in conclusion 

 briefly sum up their special advantages and disadvantages in 

 individual cases. First, in regard to carmine stainings, 

 there are two great faults which all microscopists will, I 

 think, immediately recognise. One defect is the glare of a 

 colour such as carmine, which is very tiring to the eye, and 

 renders prolonged and steady working with the microscope 

 a matter of great difficulty, not to say real injury, to the 

 eye. Then, again, the want of definition given by a deeper, 

 darker colour is felt by all experienced microscopists, and 

 more especially by those who have employed the logwood 

 and aniline dyes. On the other hand, it never clouds the 

 cell, but leaves the nuclei and all minor details clearly 

 exhibited. No one who has examined a really good pre- 

 paration of the cerebral cortex with logwood staining will fail 

 to acknowledge the great superiority of this dye over carmine 



