374 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



variable length. As the connection of the several territories of 

 the cortex must correspond to a functional connection of their 

 states of excitation, through the agency of this medullary 

 system, its fasciculi may be termed a connecting system (Asso- 

 ciationssytem). 



A fourth collection of medullary fasciculi belonging to the 

 cerebral hemispheres consists of those forming a connection 

 between the cortex of the cerebrum and the cortex of the 

 cerebellum, which are collected in the superior peduncle of the 

 cerebellum as a distinct band, situated superficially in the back 

 of the pons ; but from the intermediate nature of the course of 

 these fibres between the two cortical substances, as well as 

 from their long and close connection with the projection system 

 of the cerebrum, it is impossible in such a general description 

 as the present to give a clear notion of them, or to disentangle 

 their relations. 



The grey masses below the cerebral hemispheres (excluding 

 from the second head the grey substance of the central cavities 

 or tubular mass of grey matter) are : 



1. Interruption masses of the projection system, and 



2. Region of reduction of the mass of this projection system. 

 Here the size of its first link, the great bulk of which (chiefly 

 in the form of the corona radiata) enters the complex masses of 

 the cerebral ganglia, becomes diminished to the inconsiderable 

 dimensions of the columns of the spinal cord. 



The reduction of the projection system in its course below 

 the cerebral lobes does not. affect the total number of fibres 

 alone, but also the number of the special fasciculi that can be 

 distinguished within its substance. 



The first link of the projection system breaks up, at its point 

 of entrance into the ganglia, into as many separate special 

 Amasses as there are grey nuclei in the latter. Of such grey 

 nuclei there are exhibited in figs. 230 232, the corpora 

 striata and the lenticular nuciei (Cs) (corpora striata externa), 

 with the radiated mass of fibres (PJ ; the optic thalarni (Th), 

 and the corpora quadrigemina (Qu), with the radiated mass of 

 fibres PI and Br) ; and the distinct fasciculus of the fornix (/), 

 which is the projection fasciculus of the cortex for the anterior 

 eminence of the optic thalami. Whilst the upper link of the 



