NEW PROCESS FOR EXAMINING THE BRAIN STRUCTURE. 183 



A large amputating knife answers well for this purpose. 

 The sections should be cut in the direction from the operator. 

 As they are made they should be wiped off the blade with 

 the brush, and allowed to fall into a vessel containing about 

 half a pint of water. 



The fixing of the brush in the position described will be 

 found to give very important assistance. The piece of brain, 

 as freshly taken from the subject, is difficult to seize and to 

 hold in one position while making the slices as described, 

 and the attempt to hold the brush and the brain at the same 

 time will be found to be a work of difficulty ; and as it is 

 desirable to take several sections from the same place, the 

 piece must not be allowed to slip from the operator's grasp, 

 as it would be very difficult to readjust it. 



II. The next stage is to subject the sections to the action 

 of the dye. The water in which the sections were placed is 

 to be poured oif, until there remains only just enough to 

 cover them. To this there is to be added an equal quantity 

 of a one per cent, solution of the dye, so that in fact the sec- 

 tions will be now in a solution containing half per cent, of 

 the dyeing material. 



The Dye. — The material that I have found most satisfac- 

 tory in its effects is called aniline blue black. It can be 

 obtained from Messrs. Hopkins and Williams, Cross Street, 

 Hatton Garden. In the dry state this material is a blackish 

 powder, not unlike gunpowder in appearance. It is very 

 soluble in water, to which it imparts an intense purple colour. 

 Its chemical composition is, I believe, not exactly known. I 

 regard the use of this dye as an essential part of the process. 

 I have experimented with some thirty or forty other dyes, 

 but have had no results at all equal to those obtained by 

 aniline black. It is also useful for sections made after the 

 usual process of hardening, &c. 



The sections should be allowed to remain in the dye for 

 about twelve hours; twenty-four or even thirty-six hours' 

 immersion does not, however, often injure them. The next 

 step is to pour off the dye, and add clear water until all the 

 colouring fluid has been washed away. The stained sections 

 may be poured, with the water they are in, into a large shal- 

 low basin, and each slice floated into the middle of a glass 

 slide, and removed carefully from the water and allowed 

 to drain. As each section in this stage should be marked, 

 I can recommend for the purpose a very convenient slide, 

 invented by Mr. Hicks, and described by him in ' Quart. 

 Journ. Microsc. Science.' In this slide the portion on which 

 the label is usually gummed is of ground-glass, and wiil 



