2 NERVOUS SYSTEM OE REPTILES AND BATRACHIANS. 



I would suggest, however, to those who may feel dis- 

 posed to regard these cells as connected with the sense of 

 hearing, that such a view involves giving to this apparatus, 

 in its central portion, a structure almost identical with one 

 universally admitted to be motor, like, for example, that 

 concerned in raising the lower jaw ; whereas in the central 

 structures for vision and olfaction the cells are all very 

 small. 



Moreover, these large cells, found in the vicinity of the 

 acoustic nerve in some lizards, turtles and serpents, are not 

 found at all in the frog, while in the alligator their posi- 

 tion indicates that they may be related to the motor 

 branch of the fifth pair or possibly to the branch which 

 supplies the depressor muscles of the lower jaw. The em- 

 inentia acoustica in the latter animal swarms with uniformly 

 small cells and nuclei which are very probably the sole cen- 

 tres for the acoustic nerve, and in the same relative plane 

 the same numerous groups of small cells can be seen in 

 frogs and some lizards. 



During the past summer, through the kindness of Prof. 

 S. F. Baird, of the Smithsonian Institution, quite a num- 

 ber of valuable specimens have been placed at my dis- 

 posal, among which may be mentioned Heloderma Suspec- 

 tum, several serpents and one large example of Chelydra 

 Serpentina. 



Nuclei of the cells of the inferior (anterior) horns of the 

 caudal, lumbar, dorsal, cervical and upper cervical regions 

 of the spinal cord, in a large number of frogs of three 

 species, two species of emys and two of land turtles, and 

 in several alligators and lizards, including heloderma, 

 have been measured. Of those found in the cervical and 

 lumbar enlargements enough has been written already in 

 the two preceding papers. The preponderance in average 

 size is here in striking accord with that of the power of the 



