292 ^ournnl of Cojjiparntivc Neurology mid Psychology. 



out in order to clear up this point. The only nerve hitherto known to 

 8U23ply the nasal nuicosa in the dogfish is the olfactory. It has long 

 been known that the ti-igeniinus nerve snpplies this region of the head 

 for tactile sensation, l)nt none of its fibers have been traced to the 

 olfactory eaj)snle. 



Aichel ('95) fonnd ti'igeniinal fibers in the olfactory mncoiis mem- 

 brane of embrj'onic telcosts, bnt was uncertain as to their derivation. 

 Jagodowski ('01) observed the same fibers. Later, Sheldon ('08) 

 demonstrated the existence of fibers, derived from the trigeminal 

 nerve, in the mucous membrane of the adult cai-p. Eetzius ('92) in 

 the frog and Rnbaschin {'iVZ) in the chick obtained similar results. 

 In the lower mammals and man such an iiniervation has been demon- 

 strated by Grassi and Castronovo ('SO), Eamun y Cajal ('89, '93), 

 van Gehuchten ('90), von Brunn ('92), von Lenhossek ('92), 

 Retzius ('92), Disse ('94) and Read ('08). 



In the dogfish the trigeminal nerve is divided into four rami. 

 These are the ophthalmicus superficialis to the dorsum of the snout, 

 closely associated with the ophthalmicus superficialis facialis of the 

 lateralis system ; the ophthalmicus profundus to the side of the head 

 and snout; the maxillaris to the upper jaw and the mandibularis to 

 the lower. These latter two are bound together for some distance 

 from the brain in close association also with the buccalis. All of 

 these trigeminal rami are general sensory with the exception of the 

 mandibularis which is coml)ined general sensory and motor (Strong, 

 '03). The relations of all these rami except the ophthalmicus super- 

 facialis are shown in fig. 3. 



The olfactory crura were first cut in an endeavor to destroy the 

 sense of smell. At first the section was made from the dorsum, but 

 this operation was usually fatal. Such fishes would either die inside 

 of twenty-four hours or else react very feebly. Finally the method 

 of Lyon ('00) was adopted. The fish was etherized, the mouth pried 

 open as far as possible and the olfactory crura reached -by means of 

 an incision in the roof of the mouth. The maxillaris and mandibu- 

 laris were also reached in the same way (see fig. 3). Before the cnt 

 was made the mucosa was reflected as shown in the figure, then a 

 piece of cartilage was removed, care being taken not to cut any of the 



