183 H. R. OCTAVIUS SANKEY. 



varies from one egg to another. In all the eggs of Cheirop- 

 tera containing two pronuclei which I have examined, each 

 of these elements contained a single nucleolar element.' 

 These variations in the number of the nucleoli have also been 

 pointed out by Auerbach in Nematodes, and by Strasburger 

 in Ascidians. 



A New^ Process for Examining the Structure of the 

 Brain. With a review of some points in the Histology 

 of the Cerebellum. By H. R. Octavius Sankey. 

 (With Plate XIV.) 



The methods usually adopted in the microscopical exami- 

 nation of the brain have all proved in my hands more or less 

 unsatisfactory. I find that when thin sections of hardened 

 brain are cut and stained, the dye does not sufficiently dif- 

 ferentiate the various structures so as to render their form 

 and arrangement obvious, while in teased preparations the 

 shape of the cells, the connection of their processes, and the 

 fibres of the brain are just as likely to be torn to pieces as to 

 be separated from the substance which surrounds them. 



The plan which I am about to describe will, I think, be 

 found to overcome, to a certain degree, several of these de- 

 fects. The dye which I employ causes the nuclei to appear 

 black ; the cells and their processes are rendered dark purple, 

 while the rest of the section is of a faint purplish-blue colour, 

 so that the processes and fibres are rendered by these means 

 extremely distinct, and may often be readily traced to dis- 

 tances of a quarter or half an inch, and in some cases even 

 to greater length. 



For the sake of clearness of description I will divide my 

 process into several stages : — 



I. The first stage consists in making slices of brain, which 

 should be made from the organ as it is obtained from the 

 post-mortem room, neither hardened nor altered in any way 

 by reagents. The sections should be cut as thin as practi- 

 cable, but slices of one eighth of an inch in thickness will 

 not be found too thick for the subsequent treatment. I find 

 the following a convenient mode of making such sections. 

 A large brush is to be fixed to the back of the left ring-finger 

 by means of two elastic bands ; the operator then holding a 

 piece of brain in the left hand, slices it with a large knife 

 kept constantly wetted with spirit by means of the brush. 

 ' Edouard Van Beneden, ' De la Maturation de I'CEuf.,' &c., p. 18. 



