4 ANATOMY OF THE CENTRAL NERVOUS SYSTEM. 



formis, the insula, and many other structures were incorporated into 

 anatomy only after his investigations. 



As a landmark at the beginning of this earlier period stands Burdach's 

 book, — "On the Structure and Life of the Brain," — in which, appearing 

 in 1819, the author had carefully collected everything which had been 

 accomplished up to that time and added much explanatory matter. 



Up to about the middle of this century the technique consisted, for 

 the most part, of gross dissection with the knife and of the separation of 

 the fibers of hardened pieces of brain-tissue with the forceps. Gall, Bur- 

 dach, Eeil, Arnold, and Foville discovered much with the use of such 

 methods. 



It is especially due to Tiedemann and Keichert that, through embry- 

 ology, the general morphological relations came to be better understood. 



But since Ehrenberg (1833) had demonstrated that the brain (Seelen- 

 organ) is composed of innumerable very fine tubes, since Eemak (1838) had 

 described the ganglion-cells more exactly, and Hannover (1840) had 

 demonstrated their connection with the nerve-fibers, it was clear that a 

 simple dissection of the brain and cord was not sufficient to yield the 

 desired insight inco their structure and relations. 



Stilling's great contribution was the introduction and use of a new 

 method: the preparation of thin sections, or, rather, serial sections, which 

 were made in different, but definite, directions through the organ.^ 



The preparations so made were carefully studied, their pictures com- 

 bined, and thus the architecture of the central nervous system was recon- 

 structed. Through these methods and through the studies which he made 

 with their help. Stilling laid the foundations for the modern anatomy of 

 the spinal cord, the medulla, the pons, and the cerebellum. On January 

 25, 1843, Stilling allowed a piece of cord to freeze in a temperature of 

 — 16° C. (3° F.), and then made, with a scalpel, a fairly-thin cross-section 

 of the same. "When I brought this under the microscope," he writes, "arid 

 with 15-diameters' magnification beheld the transverse commissural fibers, 

 I was conscious of having found a key which unlocked the secrets of the 

 wonderful structure of the spinal cord. Archimedes did not more joyfully 

 shout 'Eureka' than did I at that sight." 



Stilling's method is the one still most used for the study of the central 

 nervous system. Its application is much facilitated by the hardening of 

 the nervous tissue through dilute chromic acid or solution of chrome-salts: 

 a procedure introduced by Hannover and Eckhard. The sections are 



'Eolando had previously made thin sections of the central nervous system 

 (1824), but the reconstruction of the organs through combinations of extended 

 series of sections is due particularly to Stilling. 



