CoGHiLL, Cranial Nerves of Trito77. 257 



THE NINTH AND TENTH NERVES. 



/. The Roots and Ganglia. — As to general morphology 

 Druner has correctly described the ganglia of the glossopharyn- 

 geus and vagus and the nerve trunks which arise from them. The 

 composition of the roots and trunks of these nerves, however, 

 demands some further definition. 



The roots which correspond to my second, third and fourth 

 vagus roots of Amblystoma are variable in their arrangement 

 relative to each other, but always exhibit more compactness than 

 in larval Amblystoma — a peculiarity due, no doubt, to the adult 

 condition and of no morphological significance. But in my 

 specimens which show the origin of the roots most clearly one fact 

 of importance is clear: There are no motor axones in the general 

 cutaneous root of the vagus. This can not be stated as a universal 

 condition, but it is certainly true in some indviduals, while no 

 positive exceptions have come under my observation. This would 

 appear at first thought to be essentially different from the condition 

 described for Amblystoma ('02, Plate I, X 3), but in all probabil- 

 ity the motor axones figured in m}- third vagus root of Amblys- 

 toma belong to the fourth root, as was stated in my original descrip- 

 tion ('02, p. 234). This being true, the general cutaneous root of 

 Triton and Amblystoma aHke would be unaccompanied by motor 

 axones. 



In composition, the nerves which arise from the IX-X gan- 

 glionic complex of Triton correspond exactly with those of Amblys- 

 toma. This can be positively stated for all but the niotor com- 

 ponents, w^hich can be differentiated from the sensory neurones 

 within the ganglia only in very young specimens. As these were 

 not accessible to me I have been unable to follow the motor axones 

 through the ganglia of Triton successfully, as I have done in Am- 

 blystoma. But the exact resemblance of the two types in respect 

 .to the other features of these nerves would seem to justify one in 

 assuming that the motor components of the two forms, also, would 

 follow the same laws of distribution. 



2. The Truncus Glossopharyngeus. — There are no general 

 cutaneous fibers in the root of the glossopharyngeus, but this 

 component enters the trunk of the nerve from the ganghon of the 

 vagus. These fibers usually enter the nerve within the ganglion 

 and are hard to identify with certainty. In one case, however, 



