326 G. E. COGHILL 



Figs. 47, 48, 49 Coiled-reaction stage (No 449, sections 1-6-17, 18, 19). X 500 

 Three successive serial transverse sections through the brain at the level of the 

 entrance of the root of the vagus nerve. Figure 47 is the most rostral of this 

 set: In it the visceral sensory root of the vagus (R.Vis.X) is approaching the 

 brain surrounded by cells of the root mass {R.M.), and the fasciculus solitarius 

 appears in two clusters of fibers {Fas. Sol.), a more dorsal representing the facial 

 and glossopharyngeal portion and a ventral consisting of ascending fibers of the 

 vagus root. This figure, as well as the following, extends ventrad to show the 

 relation of the sensory centers to the motor column (FT), and the visceral motor 

 nucleus {Nuc.vis.vi.). The root fibers of the vagus enter in figure 48, and in the 

 following figure a few descending root fibers can be recognized {Fas. Sol.). 



Fig. 50 Early swimming stage (No. 567, section 2-1-19). X 500. From a 

 transverse section through the medulla oblongata 35 m caudad of the entrance 

 of the trigeminal nerve. Around the dorsal margin of the descending trigeminal 

 tract {Tr.Des.V) is a cluster of three or more large neurones {DG) of the giant 

 ganglion cell type. Their processes run ventrad towards the motor nucleus 

 of the trigeminus {Nuc.vis.vi.). 



