Literary Notices. xli 



chrome coloration is a genuine staining of the interior of the nerve- 

 process ; for along the gap betwixt two separated fragments of the 

 process, we often observe an extremely delicate margination, as 

 though of a more extensile, sheath-like investment, from which the 

 stained contents have retracted and split across. Should the section 

 itself be undul)' thick, the subsequent process tends occasionally to 

 cause also slight conchoidal fractures near the margm of the sec- 

 tion as it dries ; this, however, can be avoided by employing thin 

 sections only. It is useless to dehydrate by alcohol, and mount in 

 balsam, since the shrinking entailed in the former after the action of 

 potash is extreme, and ruins the preparation. Such sections must be 

 dried on the slide and mounted in xylol balsam. The dendrites and 

 neurons are well seen in these preparations, the fine bulbous projec- 

 tions along the former being uninjured, whilst the whole cerebral 

 tissue is unfolded. 



** If, now, in lieu of using specimens prepared by the quick silver- 

 chromate, we harden in the sublimate fluid of Cox, we entirely obvi- 

 ate the disadvantages of the above procedure; the sections are not ex- 

 panded by the potash ; they undergo to a still greater degree the differ- 

 entiation of staining seen in silver-chrome preparations ; they can be 

 mounted, after dehydration Dy spirit and clearing in clove oil, in bal- 

 sam ; and undergo no undue shrinking, and present no injuries to the 

 delicate nerve processes. Cox's fluid is a modification of the subli- 

 mate method of Golgi, and is highly spoken of by Cajal.^ Brain cor- 

 tex requires immersion in this fluid for two to three months ere it is 

 sufficiently stained for our purpose. The pieces are then well washed 

 in alcohol for half an hour to remove superfluous sublimate ; the cut 

 sections are cleared in clove oil, and mounted in balsam. One great 

 advantage of this solution is the absence of much diffuse staining, 

 as shown by the silver-chrome method, the background being a pale 

 yellow hue. 



"Now, if one of these sections be treated similarly by liquor 

 potassae, an immediate darkening of the tissue elements is observed 

 by the naked eye, and tissue which, prior to this treatment, remained 

 unstained, now starts out in bold relief; so that sections prepared 



' See his remarks in "Les Nouvelles Idees sur la Structure du Systeme Ner- 

 veux," p. 185. Cox's fluid consists of — 



5 per cent, solution of bichromate of potash . 20 parts. 

 5 " " bichloride of mercury . 20 " 

 5 «« " chromate of potash . 16 " 

 Distilled water 30 to 40 " 



