Herrick, Cojntnissura Infima. 419 



Lepidosteus and it terminates for the most part in the cephaHc 

 part of the funicular nucleus. 



For my preparations of the brain of Lepidosteus I am again 

 indebted to the kindness of Professor Brookover. 



CONCLUSION 



In effecting the functional analysis of the somatic and visceral 

 centers at the lower end of the medulla oblongata difficulty has been 

 experienced on account of the diffuse character of these nuclei and 

 their tracts and the intricacy of their interrelations. At the time 

 of the publication of my report on the central gustatory paths in 

 fishes (1905) these relations were very imperfectly understood. 

 Further comparative study showed that different fishes exhibit 

 very unequal degrees of development of the somatic and visceral 

 elements in the funicular nucleus region and that by comparing 

 types with the maximal visceral elements, like the carp, with those 

 showing maximal development of the tactile system, like the 

 gurnards, the obscurity was largely cleared up, and forms with an 

 approximately equal development of both systems could then be 

 understood. 



For the convenience of the reader I have presented these results 

 in the reverse order of that adopted in the research, having pub- 

 lished the findings in Ameiurus (1906) before those in the more 

 highly specialized species, like Cyprinus and Prionotus. The latter 

 type has proven especially helpful, since, while the braui is no- 

 where very highly specialized, the spinal tactile path is greatly 

 enlarged and may therefore be isolated for study simply by com- 

 parison with other unmodified types of fishes. Accordingly I 

 have made a more detailed examination of this species (1907a). 

 In the present paper I have brought together the data scattered 

 through my previous articles so far as they bear upon this region, 

 together with some new observations on these and other fishes. 



It appears that the commissura infima of fishes (Haller) and of 

 mammals (Cajal) and its nucleus, so far from being a purely 

 visceral structure, as believed by recent critics, has an important 

 somatic sensory component, which in some fishes far exceeds in 

 size the visceral element. The visceral commissure and its nucleus 

 are extensions of the deep layer of the vagal lobes (nucleus inter- 

 medius vagi) and also of an imperfectly known visceral zone of the 



