HISTORY AND METHODS OF INVESTIGATING. 3 



whole series of sections, which are made in different but in definite 

 directions through the organ to be examined.* 



The sections so prepared were carefully examined through- 

 out, the pictures they presented combined, and thus the structure 

 and arrangement of the central nervous system were determined. 

 By means of this method and the studies which he instituted by 

 its use, Stilling laid the foundation of the modern anatomv of 



o 



the spinal cord, the oblongata, the pons, and the cerebellum. 

 On the 25th of January, 1842, Stilling froze a piece of spinal 

 cord at a temperature of 13 R., and then, with a scalpel, made 

 a moderately thin cross-section. "When I placed this under 

 the microscope," he writes, " and, with a power of 15 diam., 

 saw the beautiful transverse striations (central nerve-tracts), I 

 had found a key which would reveal the mysteries of the wonder- 

 ful structure of the spinal cord. Not more joyfully did Archi- 

 medes cry out, ' Eureka !' than I, at the first sight of these fibres." 



Stilling's method is the one now most used in investigations 

 of the central nervous system. It is rendered very much easier 

 by the splendid hardening which these organs undergo in dilute 

 chromic acid, or in a solution of chromic salts, a discovery of 

 Hannover and Eckhardt. 



The sections are made " free-hand," with a razor, or, better, 

 with a microtome, which cuts much more exactly and enables 

 us to make larger and more even sections. Welcker. Rivet, 

 Weigert, Thoma, Gudclen, Schiefferdecker, and others have 

 been of service in constructing microtomes adapted to the 

 purpose. We can now divide an entire human brain into an 

 unbroken series of sections, less than -^ millimetre in thickness. 



V 



These sections may be examined unstained. All that 

 Stilling discovered was found in such unstained sections. It is 

 better, however, to use staining fluids. 



To Gerlach is due the credit of first calling attention (1858) 

 to the advantages to be derived from staining the sections in 



*Thin Sections of the central nervous system had been made before Stilling's time (e.g., 

 B. Rolando, 1824), but the reconstruction of the organ by the combination of extended seriesx>f 

 sections was first done by Stilling. 



