431= THE FUNCTIONAL RELATIONS OF THE 



essentially parallel function, since its fibres also serve to 

 connect similar convolutions on the two sides viz., some 

 of those situated in the Temporal Lobes. A similar 

 function must also be assigned to the 'Psalterial Fibres,' 

 which in part constitute the posterior bent portion 

 (' genu') of the Corpus Callosum itself (p. 443, notet). 



These transverse ' commissural ' fibres are of much 

 interest, because there is reason to believe that they are, 

 to a considerable extent, in relation with that unification 

 of Consciousness which unquestionably exists (as everyone 

 can testify) in spite of the fact that the organs of Sen serial 

 Activity are double throughout. Such Commissures are 

 also, in all probability, very essential for the carrying on 

 of the higher mental processes. In cases recorded by 

 Dr. Langdon Down and others the non-development of 

 this part of the Brain in human beings has been asso- 

 ciated with more or less marked Idiocy ; but then, the 

 arrest of development has for the most part not been strictly 

 limited to the Corpus Callosum. The Middle Commis- 

 sure, the Fornix, or some convolution al regions have been 

 often at the same time deficient. In some of the recorded 

 cases in which the Corpus Callosum has been only partially 

 absent, there has been less degradation of the Intellectual 

 Powers than might have been anticipated. In certain of 

 these latter cases, however, the persons have either died 

 so young, or the morbid conditions have been so com- 

 plicated, as to make them of comparatively little value 

 for settling the question as to the real importance of the 

 Corpus Callosum in the carrying on of mental processes.* 

 According to the anatomical data furnished by Broad- 

 bentf it is the Sensorial Ptegions of the two hemispheres 



* See Knox, in " Glasgow Medical Journal," April, 1875, where 

 fifteen cases are referred to. 

 f See p. 442. 



