MEDULLA OBLONGATA. I 4 



described as lying within the raphe, which is httle developed in turtles, 

 and forms apart of what he calls: "the inferior median extension of 

 gray substance." 



Plate LVII. shows, roughly, the shape of the medulla oblongata of 

 the gopher turtle. The inferior portion of the septum corresponds with 

 the median extension of "gra}'" substance. It is easy to find here the 

 "nucleus basilaris" and follow it as far foi-ward as the fifth pair of nerves 

 where the cells are the largest. 



Cells somewhat similar to those in the raphe of the alligator, I have 

 found in that of skinks, anolis, heloderma and the iguana, in all saurians, 

 the raphe being well developed. The situation and form of a group in 

 serpents, closely answering to the "nucleus basilaris" are shown in 

 Plates LIV. & LV. 



In fact, Plate LIV. is a representation of three groups on either 

 side of the raphe in a species of black snake, which are probably the ho- 

 mologues of those observed by Stieda in turtles and which he called : 

 "nucleus basilaris," "nucleus centralis" and "nucleus lateralis." 



The inferior group of the nucleus centralis, in the turtle, is well 

 shown in Plate LVI. in, and is seen to differ from the superior group, in 

 the constant lateral direction of its cell processes. I have found both of 

 these divisions of the nucleus centralis — a name first given b}- Reissner 

 to a similarly situated group in the frog — in the alligator, heloderma 

 and iguana. Under Plate LI., I have ventured to suggest the possible 

 relation of this centre to the vagus. It is perhaps more probable, that 

 the cell column, which extends from the anterior bundles of the spinal 

 accessor}', as far as the anterior bundles of the vagus, contains all the 

 cells of origin of both the vagus and hypoglossal nerves ; the cells of the 

 spinal accessoi-y lying behind. See Plate XLVII. 



I have been unable to trace the hypoglossal roots to an}- distinct 



