Chap. XXIIL] OF THE HUMAN BRAIN. 4o3 



discussed — partly, moreover, because his observations seem 

 to tbe writer to have been conducted with great care, and 

 also to have been interpreted from a correct general 

 standpoint. Thus, though the investigations of Broadbent 

 have as yet only been published in abstract,* they 

 will principally be cited in this and in the following 

 sections. 



One of the most fundamental facts in regard to the 

 structural relations of the Cerebral Hemispheres and 

 their Peduncles, is that the left half of the Brain is 

 specially in connection with the right half of the body, 

 and the right half of the Brain with the left half of the 

 body. This arrangement exists not only in Man, but in 

 Venebrates generally (though with varying degrees of 

 completeness), and it is due to the fact that the 'ingoing' 

 fibres to each Cerebral Hemisphere come from, whilst its 

 * outgoing ' fibres are distributed to, the opposite half of 

 the body. 



Speaking in general terms, it may be said that the 

 'ingoing' fibres which enter the Cord and Medulla on either 

 side throughout their whole length, soon cross over, as 

 Brown- Sequard has shown, to the opposite side of these 

 centres ; and that they thence follow an ascending course 

 towards — though they do not necessarily go as far as — 

 the Cerebral Hemisphere of the same side. Similarly, 

 an important section at least of the ' outgoing ' or motor 

 fibres, viz., those forming part of the ' anterior pyramids ', 

 decussate with their fellows in the Medulla, so as to pass 

 over to the opposite ' lateral column ' of the Cord. Thus, 

 even allowing for the fact that some of the Cranial Motor 

 Nerves decussate by themselves higher up, in the sub- 



* " The Structure of the Cerebral Hemisphere," Journal of 

 Mental Science, 1870 ; aud also "The Construction of a iSI'ervous 

 System," JBiit. Med. Joiirn., March & April, 1876. 



