THE STORY OF NINETEENTH-CENTURY SCIENCE 



The common ground of all these various lines of in- 

 vestigations of pathologist, anatomist, physiologist, phys- 

 icist, and psychologist is, clearly, the central nervous 

 system the spinal cord and the brain. The importance 

 of these structures as the foci of nervous and mental ac- 

 tivities has been recognized more and more with each 

 new accretion of knowledge, and the efforts to fathom 

 the secrets of their intimate structure has been unceas- 

 ing. For the earlier students, only the crude methods 

 of gross dissections and microscopical inspection were 

 available. These could reveal something, but of course 

 the inner secrets were for the keener insight of the mi- 

 croscopist alone. And even for him the task of investi- 

 gation was far from facile, for the central nervous tissues 

 are the most delicate and fragile, and on many accounts 

 the most difficult of manipulation of any in the body. 



Special methods, therefore, were needed for this essay, 

 and brain histology has progressed by fitful impulses, 

 each forward jet marking the introduction of some in- 

 genious improvement of mechanical technique, which 

 placed a new weapon in the hands of the investigators. 



The very beginning was made in 1824 by Rolando, 

 who first thought of cutting chemically hardened pieces 

 of brain tissues into thin sections for microscopical ex- 

 amination the basal structure upon which almost all 

 the later advances have been conducted. Miiller pres- 

 ently discovered that bichromate of potassium in solu- 

 tion makes the best of fluids for the preliminary preser- 

 vation and hardening of the tissues. Stilling, in 1842, 

 perfected the method by introducing the custom of cut- 

 ting a series of consecutive sections of the same tissue, 



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