NERVES OF THE DOGFISH 



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Landacre to the extent that the first rootlet of the portio minor 

 may contain sensory elements from the profundus ganglion. 

 But the first rootlet also contains motor fibers that pass directly 

 into the lateral motor column. The mesencephalic V tract may 

 contain sensory fibers, but sensory fibers entering through the 

 first rootlet of the portio minor may possibly all enter the spinal 

 V tract. Johnston ('05, '09), who argues for the sensory nature 

 of the radix, says that it passes out of the brain by the sensory 



root, portio major. This is certainly an error, for both in 

 Squalus and Scyllium (van Valkenburg) it passes by way of the 

 first rootlet of the portio minor. The portio minor is pre- 

 eminently the motor root of the trigeminus in the selachians. 

 Though the material used by the writers does not warrant the 

 statement that there are no sensory elements in the radix, it 

 does lend support to the view that the radix is an efferent tract, 

 at least in part. As Allen ('19) has recently concluded, the radix 

 mesencephalica trigemini is possibly concerned functionally 

 with the muscle sense. 



