Herrick, Medulla Oblongata of Fishes. 419 



in the dorso-lateral fasciculus, which arises in the dorsal cornu and 

 terminates chiefly in the funicular nuclei but partly in the formatio 

 reticularis of the oblongata farther cephalad. 



The two funicular nuclei, then, and the spinal V nucleus to- 

 gether represent differentiations of the somatic sensory column of 

 the spinal cord. They have little, if any, direct connection with 

 the phylo genetically ancient visceral sensory centers represented 

 in the commissural nucleus of Cajal and the vagal lobes. They 

 do, however, receive the secondary gustatory tract from the facial 

 lobes, this being a connection recently acquired by these highly 

 specialized fishes to eff^ect a cerebral connection between the long 

 established tactile organs of the skin and taste buds which have 

 later appeared in these same cutaneous areas. The facial lobe 

 is known to receive all of the peripheral nerves from these 

 cutaneous taste buds and it is the only visceral center which is 

 closely connected with the somatic sensory centers of the medulla 

 oblongata. The gustatory fibers from within the mouth terminate 

 in the vagal lobes and have no such intimate relations with the 

 somatic sensory centers. The descending secondary gustatory 

 tract from the facial lobe must, then, be regarded functionally as a 

 somatic reflex path, even though morphologically it belongs to the 

 visceral division of the nervous system; for it is excited only by 

 gustatory stimuli arising in the outer skin and accompanied ordi- 

 narily by simultaneous tactile stimuli. Moreover, it terminates in 

 the primitive tactile coordination center of the brain, which suffers 

 but little modification in consequence, and the motor return paths 

 for the tactile and the gustatory stimuli seem to be identical. The 

 last point is correlated with the fact that experiment shows that 

 identically the same somatic reactions follow from either tactile 

 or gustatory excitation of a given area of skin, though the fish may 

 be taught to react to one and not to the other bv training (Herrick, 

 '04). 



summary 



The analysis of the lower region of the medulla oblongata and 

 upper region of the spinal cord in Ameiurus shows that the visceral 

 and somatic divisions are as clearly separable here as in other parts 

 of the central nervous system. The visceral sensory zone is ill 

 defined in the spinal cord, but in the oblongata is concentrated into 

 three massive structures. The lowest, the commissural nucleus of 



