298 



ANATOMY OF THE CENTRAL KEEVOUS SYSTEM. 



nerve (see especially Fig. 195). It receives a bundle from the arm of the 

 corpus quadrigeminum anterius, well sho\vn on the left side of the figure, 

 above which one will recognize the corpus geniculatum mediale. Beneath 

 the pulvinar the pes peduncuU emerges. 



In the pes are contained fibers of very varied origin. Embryological 

 studies and especially the exact tracing of secondary degenerations, which 

 result from cerebral lesions, alone make it possible to determine where the 

 difl^erent tracts lie. There is already a considerable number of well observed 

 cases of partial degeneration of the pes, so that an enumeration of the parts 

 of the pes may with due certainty be given. According to Dejerine's in- 



Fig. I'.t2. — Cross-section through the corpora quadrigeniina anteriora (some- 

 what diagrammatic) . Tordrre ]'ierhiigel, Corp. quad. ant. Arm des Tierh., Arm 

 of the Corp. quad. JIfiiilji', Tegmentum. Fuss, Crusta, or pes pedunculi cerebri. 

 ScMcifc, Lemniscus, or fillet. Biiilcres Ldnijshiiiidel, Fasciculus longitudinalis 

 post. Itotltcr Kcni, Nucleus ruber. 



vestigations, which cover the largest amount of material yet studied, there 

 lie in the outer fifth of the pes fibers ^I'hich arise from the middle part of 

 the temporal lobe. In its median fifth are fibers which pass down from the 

 region of the operculum. In the middle three-fifths of the pes are found 

 the fibers from the posterior portion of the frontal lobe and from the true 

 motor region. All of these bundles arise direct from the cortical cells and 

 degenerate when they are interrupted anywhere between the cortex and 



