BRAIN or ONE OF THE SALAMANDERS 99 



terms rather than to use [BNA] terms of doubtful application. The 

 terms of the [BNA] nomenclature as used here are from the table given 

 by Hardesty ('02) in his ^'Neurological Technique.''^ 



External Features 



In external features, the brain of Plethedon glutinosus presents no 

 striking differences from that of other Urodela. It resembles most 

 closely that of Desmognathus jusca as described by Fish ('95). It 

 measures 7 to 9 mm. in length and 2 to 2.5 mm. in width at the widest 

 part. There is somewhat of a cervical flexure which is corrected by a 

 more decided pons flexure, so that the general contour of the brain is 

 straight. The brain by no means fills the cranial cavity, the relation 

 being shown in Fig. 7. 



The widest part of the brain is near the caudal extremity of the 

 cerebral hemispheres, from which place it narrows toward the anterior 

 end of the olfactory lobes. The diencephalon lies between the diverging 

 caudal ends of the cerebral hemispheres. The mesencephalon is of 

 the usual type in Urodela. The metencephalon (cerebellum) appears 

 as a band running around the caudal end of the mesencephalon. The 

 medulla is of the regular type found in Amphibia. 



In this study no special attention was given to the meninges and 

 blood supply. So far as observed they agree with the accounts of these 

 features in other Amphibia. 



General Morphology 



Telencephalon — In this division of the brain are included the cerebral 

 hemispheres and their forward extensions, the olfactory lobes. The 

 cerebral hemispheres are somewhat cylindrical, and smaller in front 

 than near the posterior end. Their caudal ends taper abruptly. Exter- 

 nally the posterior limit of the olfactory lobes is not clearly marked. 

 It was not clear from my observations of the internal structure just 

 where the limit should be placed. The olfactory glomerules lie near 

 the surface of the antero-lateral aspect, somewhat toward the ventral 

 surface. The large olfactory nerves, here as in other Urodela, arise 

 from the antero-lateral angle of the rhinencephalon. The lateral ven- 



