189 



IX and X) in Petromyzon gave a picture of an apparently complete 

 series of nerves (T.'s Fig. 32) without the visceral sensory component. 

 Second, the author has not appreciated the arrangement of fibers in 

 the cranial nerves into systems or categories on the basis of their 

 central and peripheral connections and functions. If he had understood 

 the systems of nerve components as they have been worked out in 



ax 



Fig. 6. Part of a transverse section, left side, showing a cell of the somatic sen- 

 sory column. Magn. about 175 diam. 



amphibians (Strong, Coghill), bony fishes (Herrick, Cole) and Petro- 

 myzonts (Johnston), he could not have failed to see that one whole 

 system of components was unaccounted for in his description. 



For much the same reason, Tretjakoff's description does not 

 make clear the functional organization of the brain. The description 

 of the ventral and lateral motor columns agrees in the main with that 

 of other authors. In addition to these the author recognizes in the 



