MICROSCOPICAL EXAMINATION. 399 



3. — Float the section on to water. It should be free from 

 wrinkles; if allowed to sink beneath the surface they appear at once. 



4. — Take the section up as soon as possible with a perforated 

 lifter, drain off excess of water on blotting-paper, and float the 

 section on pure piridin.* Kept at hand in a watch-glass ; it may 

 presently be pushed beneath the surface of the liquid. Hitherto 

 I have kept sections in the piridin for at least one hour — usually 

 several hours. In one case one quarter of an hour sufficed to fix 

 the tissue-elements, so that the time above mentioned is, perhaps, 

 unnecessarily long. 



5. — Wash well in water. 



6. — Stain. 



7. — Dehydrate and clear in piridin (possibly desirable to pass 

 through piridin diluted with water into the pure reagent). 



8. — Mount in balsam suitably thinned with piridin. 



In this way sections free from wrinkles are obtained. It cer- 

 tainly may occur that out of a large number of sections some 

 present a slight fold at the point of exit of one of the nerve roots, 

 but most obtained are quite free from wrinkle. Such sections 

 are instructive, even unstained, examined simply in water upon 

 the slide. The horns stand out in relief against the darker white 

 substance, and the nerve-roots are clearly seen, sweeping outwards 

 in broad bundles. Within the horns appear large, colourless 

 ganglion cells, and an intricate meshvvork of fine nerve-tubes. All 

 these structures approach very nearly the natural size. Such fresh 

 specimens would probably show tract degenerations well under the 

 low power. In stained specimens the transverse sections of the 

 nerve-tubes in the white substance are brought out exceedingly 

 well ; the contour of the tubes is sharp ; the axis cylinders are 

 well stained. The appearance of the white column is such as one 

 is accustomed to see in sections from hardened cord ; the effects 

 of corrugation are, however, absent, and the wealth of structure is 

 greater than in the latter case. 



Any of the dyes ordinarily used for the purpose may be 

 employed for staining the axis cylinders and connective tissue of the 

 white matter, but I have mostly used anilin-blue black (^ per cent. 



* First recommended, I believe, by De Souza [Zeitschr. f. 7aiss. Mikros- 

 kopie, Bd. v., H. i) as a hardening reagent for brain substance. 



