138 Journal of Comparative Neurology. 



slightly bluish sheaths, the nuclei of the latter and of tracheae, 

 the tracts of nerve fibers and some of the association fibers, 

 clearly marked off from the surrounding ground work of fine 

 branchlets forming the Pnnktsubstanz of the older German 

 writers and the medullary substance of Viallanes. The struc- 

 ture of the cell bodies and their nuclei is also well brought out. 

 In some cases the freshly excised brains were dropped into 

 10 to 20% formol, in others they were placed in the following 

 mixture, which gave just about as good results : 



10^ Potassium bichromate, 40 parts. 



5% Sulphate of copper, 40 parts. 



Formol, . , 20 parts. 



This might be improved by leaving out the bichromate, 

 which is rather unnecessary since the formol likewise has the 

 property of rendering the components of animal tissues insolu- 

 ble in water and alcohol. 



Brains hardened in this mixture were washed for from a 

 little while to some hours in tap water, then for from a few to 

 twenty four hours in ^0% alcohol, after which they were de- 

 hydrated, imbedded in paraffin, sectioned and stained on the 

 slide in the hsematoxylin. 



In the other cases the sections of the formol-hardened 

 brains were treated with the sulphate of copper (5%). In a 

 solution of this they were left for from a few to twenty four 

 hours or in a warmed solution for from 20 to 30 minutes. They 

 were then washed off in tap water and stained. 



The hsematoxylin mixture that gives the best results 'is 

 one containing phosphomolybdic acid, though the plain alcohol- 

 water haimatoxylin used in the method of Weigert and its 

 modifications gave good results for certain details in the roots 

 of the mushroom bodies. The former mixture is that suggested 

 by Mallory and is composed as follows : 



10^ Phosphomolybdic acid i c.c. 



Hcematoxylin crystals i grm. 



Chloral hydrate . 6 to lo grm. 

 Water . 100 c.c. 



