THE CRUSTA OF THE CEREBRAL PEDUNCLE AND ITS GANGLIA. 411 



The mass of medullary substance proceeding from the olfac- 

 tory lobes to the anterior commissure is in animals much 

 larger than the radiations which pass into that commissure 

 from the medulla of the hemisphere (figs. 238, cm 2 ; 242, c). 

 The reverse occurs in Man, in whom the anterior commissure 

 almost entirely passes into the medulla of the hemispheres, 

 whilst corresponding to the feeble development of the olfactory 

 lobe is its small connection with them (fig. 241, Ca M' R). 



Thus, besides, the decussation between the olfactory lobe of 

 one side and the opposite hemisphere, which is effected by the 

 cord-like convoluted course of the fasciculi (Burdach), in the 

 anterior commissure there must necessarily also be commissural 

 fasciculi connecting together both the two olfactory lobes and 

 the two hemispheres. 



If we include amongst these the fasciculi proceeding from the 

 olfactory lobe to the corpus striatum of the same side (Clarke, 

 Walter, Gratiolet),we shall have in the medulla of the olfactory 

 lobes, which forms one body with the anterior commissure, all the 

 variations in the course of fibres that were ascribed by Johann 

 M tiller to the chiasma nervorum opticorum. Thus the ana- 

 logy between the olfactory lobes and retina is rendered still 

 more close by the presence of an olfactory chiasma corre- 

 sponding to that of the optic nerves. 



THE CRUSTA OF THE CEREBRAL PEDUNCLE AND ITS GANGLIA. 



The upper link of the projection system penetrates by its 

 peripheric extremity into a variously formed mass of ganglia, 

 which genetically belong (1) to the vesicles of the hemi- 

 spheres, and (2) to the anterior and median cerebral vesicles. 

 Each of these ganglia possesses two morphological poles ; a 

 central, which receives the upper link of the projection system, 

 and a peripherical, which gives origin to the central extremities 

 of the fasciculi of the second link of the projection system of 

 the crus cerebri. The crus cerebri, both in its crusta (Fuss), 

 and in the tegmentum (Haube), independently of the fasciculi 

 of the spinal cord arising from it, contains also a considerable 

 quantity of cerebellar fibres, which become detached from it 

 above the spinal cord. However peculiar may be the cha- 



