CHAP, ii.] THE BRAIN. 1045 



The results of stimulating the fibres of the tract in their course 

 through the corona radiata and the internal capsule, and the 

 results obtained by studying the degenerations following upon 

 injury to or removal of the several parts of the cortical motor region, 

 agree in marking out the paths taken by the several constituents 

 of the tract through the central white matter of the hemisphere, 

 the corona radiata and the capsule. Comparing Figs. 126, 127 

 with Figs. 121, 122 and 123 it will be seen that the portion of the 

 tract destined for the cranial nerves, and so for the movements of 

 the eyes, the mouth, face, tongue, pharynx and larynx, starting 

 from the ventral parts of the more frontal district of the motor 

 region, take up their position at the knee of the internal capsule ; 

 and the portion destined for those upper cervical nerves which 

 carry out movements of the head through the muscles of the 

 neck, starting from the extreme frontal and dorsal parts of the 

 area, is also apparently directed to the knee of the capsule. The 

 rest of the tract, starting from the part of the area lying at once 

 behind and mesial to the above, occupies in the capsule a position 

 posterior to them in the hind limb of the capsule ; and it will be 

 observed that the tract for the fore limb which begins on the 

 surface lateral of the tracts for the trunk and hind limb, shifts its 

 course in relation to theirs, so that in the capsule it is in front of 

 them, not lateral to them. It may further be observed that while 

 in the tracts for the trunk and hind limb the same fore and aft 

 order which obtains on the surface is reproduced in the capsule, 

 even apparently to the strange precedence of the ankle over the 

 knee, the order of the several elements in the fore limb tract 

 which is lateral on the surface becomes regularly fore and aft in 

 the capsule. In- the capsule the several elements are arranged in 

 a linear order, corresponding broadly to that of the distribution of 

 the muscles along the longitudinal axis of the body ; on the cortex 

 they are disposed in an order the cause of which is at present not 

 very clear, but which is probably determined by the respective 

 relations of the several parts of the motor region to the functional 

 activity of the other parts of the cortex. In the shifting from the 

 one order to the other, the several constituent fibres, as we have 

 said, describe a somewhat peculiar course ; and when we remember, 

 as stated in 632, that the order shewn in Fig. 121 is only the 

 order obtaining at one particular level of the capsule, and that 

 from the dorsal beginnings of the capsule in the corona radiata to 

 its ventral end in the pes, the capsule is continually changing in 

 form, and its fibres therefore continually shifting their relations to 

 each other, the whole course of the several fibres of the tract from 

 their origin in the cortex until they are gathered up into the 

 central portion of the pes (Fig. 114 Py) must be a very compli- 

 cated one. 



When the area of one hemisphere is stimulated, the movement 

 which results is in most cases seen on the other side of the body, 



