HISTORY AND METHODS OF INVESTIGATING. 9 



tracing out a fasciculus of nerve-fibres in the fully-developed 

 organ. In order to give you an idea of the peculiarities of the 

 methods just mentioned, I will first show you a specimen which 

 was obtained by teasing, and which shows the course of the fibres 

 making up the corpus callosum (Fig. 1). The accompanying 

 cut (Fig. 2) is made from a frontal section through the cerebrum 

 of a 9 months' still-born fce^us. In the adult the whole field 

 .shown here is filled with fibres, which, crossing and anastomos- 



FIG. 2. 



Frontal section through the posterior portion of the fissure of Sylvius of the brain 

 of a 9 mouths' still-born clrH i. Tim medullary fibres are shown black. In reality they 

 appear white upon a gray back-ground. 



ing with each other, cannot be traced up. In the case of our 

 foetus, however, of all the various fibres of the cerebrum, only 

 one bundle, the one called the tegmental tract, contains medul- 

 lary matter. Nowhere in the cerebrum, except at this point, 

 can we find medullated fibres. Hence, it was easy for Flechsig 

 to discover and partly trace out the course of the fasciculus 

 tegmenti as a distinct bundle among all the many little-known 

 nerve-tracts of the brain. 



