148 THE HUMAN BODY 



stitutes the auditory area. Although the paths of smell and taste 

 are imperfectly known, their cortical terminations have been 

 fairly well established. The olfactory area is supposed to be in 

 the temporal lobe, and possibly at its very tip. The area for 

 taste, gustatory area, is thought to be also in the temporal lobe, 

 probably adjacent to the area for smell. Since the nerve-paths 

 of the various senses lead directly to these areas, and since de- 

 struction of any one of them, by accident or disease, results in 

 loss of the particular sense whose area is involved, we must con- 

 clude that the sensory areas are the receiving stations of the 

 cerebrum. All afferent projection fibers entering the cerebrum 

 terminate in one or another of the sensory areas. Within these 

 areas they have synaptic connection with the association neurons 

 of the region. 



The Motor Area and the Pyramidal Tracts. In each hemi- 

 sphere a region of the frontal lobe just in front of the fissure of 

 Rolando contains numerous giant pyramidal cells whose axons 

 extend into the white matter and are grouped together in the 

 internal capsule as a conspicuous nerve tract. Because all the 

 axons of this tract arise from pyramidal cells it is called the 

 pyramidal tract. It extends through the midbrain to the medulla 

 and appears upon the ventral surface of the latter as a well-marked 

 anatomical feature. About midway of the medulla the pyramidal 

 tracts cross the mid-line in the decussation of the pyramids. This 

 decussation is not complete; part of the fibers of each pyramidal 

 tract continue along the same side of the medulla to the spinal 

 cord and down the latter in the ventral column, forming the direct 

 pyramidal tract. That part of each pyramidal tract which crosses 

 over at the "decussation" proceeds along the spinal cord in the 

 lateral column as the crossed pyramidal tract (Fig. 66). It appears 

 that most of the fibers of the direct pyramidal tracts cross the 

 mid-line in the spinal cord before reaching their terminations; so 

 that the pyramidal tracts are finally crossed tracts. All the py- 

 ramidal axons have synaptic connection, either direct or through 

 intervening association neurons, with the cells of motor neurons 

 in the ventral horns of gray matter of the cord. 



Since the pyramidal axons arise from cell-bodies within the 

 cortex it is evident that the pyramidal tracts must be efferent 

 paths. The intimate way in which the pyramidal fibers connect 



