NEW PROCESS FOR EXAMINING THE BRAIN STRUCTURE. 185 



screws, and can be raised just above the level of the cutting 

 blade of the plane. They thus forms guides, one on either 

 side of the knife, by means of which the thickness of the 

 section is regulated. In using the plane, each end of the 

 glass side is pressed tightly down on the iron on either side, 

 so that the slide bridges over the interval between the guides. 

 The dried slice of brain being on its under surface, by passing 

 the slide along the guides from front to back all the project- 

 ing portions of the tissue come in contact with the knife, and 

 are pared oif until the whole is reduced to the requisite 

 thickness, this thickness being regulated at will by raising or 

 depressing the side guides. 



V. The preparation is now to be cleared by means of 

 dammar varnish or Canada balsam. The intervention of oil 

 of cloves is not required. The section may be examined at 

 once with a low power, and, if found satisfactory, a cover 

 glass should be placed over it. 



Sections prepared as above may be made of almost any size. 

 I have some which cover an extent of glass equal to three or 

 four square inches. By employing a very long knife sec- 

 tions extending from the medulla oblongata through the pons 

 varolii into the crus cerebri, for instance, can be readily 

 prepared ; and in many of my finished preparations fibres 

 can be traced to extraordinary distances. 



I have now treated the brains of a considerable number of 

 animals by this method, and have also made a few prepara- 

 tions of the spinal cord and sympathetic and spinal ganglia 

 of the larger domestic animals, and always with more or less 

 satisfactory results. I find that the larger and older the 

 animal is, the better are the preparations which are obtained. 

 In the smaller animals the brain is softer and much more 

 difficult to cut, and it is apt to break down in the dye into a 

 ropy tenacious mass, showing no trace of the outline it pre- 

 viously presented. The brains of young and small animals 

 become also more brittle when dried, and are liable to crack 

 or contract in the process of drying. In spite of these diffi- 

 culties, however, with care sections of even foetal brains may 

 be prepared. Of all brains, that of the human adult is the 

 one for which my process is most suited, and especially, it 

 has seemed to me, in cases in which the temperature has 

 been elevated for some time previous to death. The process 

 is inapplicable to brains which have been hardened by any 

 reagent, as they will crack or become brittle in the drying ; 

 nor is it suitable for brains which have been in any fluid cap- 

 able of crystallization ; for crystals form during the desicca- 

 tion and spoil the preparations. If sections cannot be made 



