HISTOKY AND METHODS OF INVESTIGATION. 



made mostly with the microtome, which makes possible exact sectioning 

 and large sections of unvarying thickness. Faultless serial sections of an 

 entire human brain can now be prepared less than ^/jo millimetre in 

 thickness. 



The sections may be studied unstained. All that Stilling found was 

 seen in such unstained preparations. It is advisable, however, to stain them. 

 We are indebted to Gerlach (1858) for having first drawn attention to the 

 advantage to be gained through a soaking of the preparation in carmin. 

 Later times have produced many ^staining methods; especially have anilin 

 stains (nigrosin, etc.) been used. But only recently have we, through Golgi 

 (1883), found a method which accomplishes more than the old one of Ger- 

 lach. This method is based upon the action of chrome-silver: blackening 

 the cells and their processes. To it we are indebted for an entirely new 

 and unexpected insight into the finer structure of the central nervous 

 system. 



Nissl first made it possible, through careful hardening and after- 

 treatment with anilin stains, to make preparations which furnished a 

 glimpse into the structure of a ganglion-cell. The course of fibers is not 

 made much plainer through carmin staining. On the other hand, it is 

 possible, through Weigert's (1884) valuable method of hematoxylin stain- 

 ing, to stain even the finest fibers a deep blue-black, and so, following Still- 

 ing's method, trace their course more easily than was formerly possible. 

 One may also get beautiful preparations through treatment of the tissue 

 with osmic acid, following Exner and Bellonci. 



Since the time of Clarke's recommendations on this point (1851), the 

 stained sections are dehydrated in alcohol and then through an ethereal 

 oil or through xylol made transparent ("cleared"). 



In 1886 Ehrlich showed that it is possible, with methyl-blue, to stain 

 axis-cylinders and ganglion-cells of living animals. In the hands of Eetzius 

 and others this process has become of the greatest importance for the in- 

 vestigation of the finer structure of these portions of the central nervous 

 system. 



Most of the investigators who have worked upon the central nervous 

 system during the second half of this century have followed Stilling's 

 methods. 



We are indebted to two men, Stilling and Meynert, for most that we 

 know of the minute structure of the brain and cord. It is to be noted 

 that all later investigators have proceeded from that which these men 

 established. 



Benedict Stilling laid the foundation of all our knowledge of the pons, 

 the cerebellum, the medulla, and the spinal cord through a series of most 

 important works bearing testimony to unapproached industry: works which 



