THE SUBTHALAMIC REGION, ETC. 



113 



quadrigemina, and which have been cut off obliquely. They 

 pass backward in the region over the substantia nigra. These 

 fibres arise in great part from the ganglia of the corpora quad- 

 rigcmina. They are called the lower fillet. The upper fillet, 

 which arises mainly from the tegmental striation, or, rather, 

 from the ansa lenticularis, lies, at the level which we are now 

 considering, just outside of and below the red nucleus, and ap- 

 pears as a separate bundle of transversely divided fibres. To 



FIG. 05. 



A frontal section made in an oblique direction trending downward and backward 

 (direction of section shown in small figure). It contains the greater part of the origin 

 of the mid-brain fillet. Haematoxylin stain. 



Cmtr. ffiililenqrau. Central gray matter. 

 Schleifenschickt des Pans, Stratum lemnisci of the pons. 



SchniUrirJiltinij, Plane of section. 

 Tiefes Mark, Deep marrow. 



the inner and outer sides of it the fibres of the lower fillet are 

 joined to it. Thus it comes that there is a wide area of trans- 

 versely divided fibres just above the substantia nigra, and this is 

 called the layer of the fillet (stratum lemnisci). 



The greater part of the layer of the fillet can be traced caudad to the 

 nuclei of the sensory nerves and of the posterior column. Meynert first showed 

 that this was a portion of the sensory tract. Embryology and comparative 

 anatomy equally bear out this view. We shall study the course of the fillet 

 later. 



8 



