450 THE BRAIN OF MAMMALS, BY TH. MEYNERT. 



the ganglionic masses which have received the brachia of the 

 corpora quadrigemina fasciculi issue, which, inferiorly to the 

 posterior commissure, form the compact decussating medulla of 

 the middle line. From thence proceeds the indirect prolonga- 

 tion of the brachi/um of the nates, in the form of fine oblique 

 fasciculi, mingled with small elongated (18 25 fj. long and 

 5 fj, broad cells, collected anteriorly and externally in a fan- 

 shaped mass which presents a semilunar section, and which 

 is in the first instance covered by the processus a cerebello ad 

 testes, viz., the superior lamina of the fillet (lemniscus) (figs. 

 249, Te ; 250, m). From the intermixture of cells in this me- 

 dulla, which already forms a part of the tegmentum, we may 

 conclude that there is an increase in the number of the fibres 

 as it descends. 



The tegmental portion of the testes passes forwards in the form 

 of fasciculi, which, constituting the inferior lamina of the lem- 

 niscus, are covered on their external surface by a sickle-shaped 

 portion of the superior lemniscus, in great measure, however, 

 forming the free external surface of the tegmentum. By this 

 means they immediately cover the processus cerebelli ad cere- 

 brum, as it runs outwards from its median decussation at the 

 level of its origin from the corpora quadrigemina (figs. 250 and 

 251, m, S, BA). 



The organization of the tegmentum, which proceeds as a 

 compact mass in the posterior division of the pons (fig. 250), 

 is, properly speaking, still not complete in the lowermost sec- 

 tional planes of the crus cerebri, but receives an addition in 

 the uppermost planes of the pons. In the corpora quadrige- 

 mina, the breadth of the transverse section of the fillet does 

 not quite extend to the raphe, but ceases about five milli- 

 meters to its side (fig. 249, m). In the uppermost transverse 

 sectional planes of the pons this most anterior fan of fasciculi, 

 supporting as it were the remaining structure of the tegmen- 

 tum, extends to the raphe (fig. 251, m). 



This extension inwards, however, is by no means caused by 

 the fasciculi of the most superficial layers of the fillet being 

 thrust inwards, but by an additional formation, which, as 

 Stilling correctly observed, proceeds from the crusta, and occu- 

 pies the space between the raphe and the layers of the fillet. 



