Johnston, The Radix Mesencephalica Trigemini. 629 



fibers of the acustic area. In these figures the cells are removed from 

 the motor nucleus by about the diameter of that nucleus itself. The 

 cells shown in Fig. 22 are the nearest cells to the motor nucleus. 



Foetus of 37 cm., horizontal or frontal sections. From this series 

 nine sections are drawn (Figs, 23 to 32) showing the course of the 

 mesencephalic root from the mid-brain to its exit in the trigeminus. 

 For the purpose of demonstrating whether this bundle is connected 

 with the motor or sensory root it will be best to follow it from above 

 doAvnward in the description. In sections through the decussation 



Fig. 24. The sixth section of this series (12 of the whole series presumably) 

 ventral to that drawn in Fig. 23. x 20. Description in text. 



of the trochlearis the mesencephalic bundle is seen passing forward 

 deep in the corpora quadrigemina, or rather along their base, and 

 reaching nearly to the bundles of the posterior commissure. Cells 

 are seen at intervals along the bundle, twenty or more being counted 

 in a single section on one side. A drawing of such a section has not 

 been made because this part of the course of the bundle is familiar 

 to every one. Fig. 23 shows a section of the mesencephalic bundle 

 beneath the posterior eolliculus at the point where it begins to turn 

 ventrally. Far forward appears the root of the trochlearis, to the 

 left is the lateral lemniscus, and between them is the brachium con- 



