458 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



peculiar arrangement, inasmuch as they are parallel, not so much 

 to the nerve fasciculi as to the capillaries and finest arterial 

 twigs, to the walls of which they are adherent, arching over the 

 angles of division ; and inasmuch also as the long and strong 

 processes of these large nerve corpuscles (45 JJL long by 15 /UL) 

 run along with and probably within the vascular wall. This 

 character is already demonstrable in the red nucleus, and sub- 

 sequently on the other side of the point of decussation, the 

 superior peduncle first becoming free from nerve corpuscles 

 below the corpora quadrigemina. Thus, in the central organs, 

 the cerebral capillaries appear to constitute a sort of peripherical 

 surface for the termination of the cell processes, and further 

 research is required to show whether the portion of the superior 

 peduncle included in the eras cerebri be the only field for this 

 kind of relation. 



The medullary area of the superior peduncle approaches 

 very closely to the raphe, but never appears as a simple un- 

 mixed transverse section, being already at the above-men- 

 tioned level, anteriorly to the inferior half of the nates, 

 mingled with a large number of transverse strise, in which 

 portions of the superior peduncle, seen in transverse section, 

 curve round in order to pass from the right to the left side, 

 and vice versa, decussating with one another. The decussation 

 lies between the posterior longitudinal fasciculi and the layers 

 of the fillet, the remaining fasciculi of the tegmentum for the 

 spinal cord having all been pressed outwards by the connect- 

 ing arm. Proceeding from the decussation, the fasciculi of the 

 superior peduncle pass outwards as far as to the internal surface 

 of the inferior fasciculi of the fillet (coming from the testes), 

 which consequently form the investment of the decussated 

 superior peduncle. 



The more the decussation of the superior peduncle, and the 

 formation of the crossed superior peduncle (which occurs in 

 the region of the lower half of the testes, and of the emergence 

 of the trochlearis) is completed (figs. 250 and 251, A), by so 

 much the more is the point of decussation concentrated in the 

 anterior half of the back or posterior division of the pons. 

 The superior peduncles of both sides thus form a horse-shoe 

 closed in front, in the posterior opening of which is enclosed 



