i8o Journal of Comparative Neurology, 



Innervation of the Olfactory Epithelium. 

 By A. D. Morrill. 



Hamilton College. 



The innervation of the olfactory organ is of interest as it 

 is the only sense organ, in vertebrates, where continuity of the 

 nerve-fibers with the sensory cells exists, according to the large 

 majority of investigators. 



The statement by Dr. Ayers that the relation of the nerve 

 fibers to the sensory cells was the same in the cochlea of the 

 pig as in the olfactory organ of vertebrates led me, after study- 

 ing the relation of the fibers and sensory cells in the ampullae 

 of the ear of the smooth dog-fish, to try the same methods with 

 the olfactory organ of this fish. 



In the ampuUse, with Ehrlich's method, I found contact 

 and free endings but no case which seemed to be true continuity. 

 In the olfactory organ I found continuity and some some free 

 endings but nothing that resembled the relations found in the 

 ampullae. 



I found the three types of cells described by Dogiel in his 

 paper on the olfactory epithelium of the sturgeon : ist, spindle- 

 shaped ; 2nd, cylindrical with a slight constriction near the 

 middle; 3rd, conical, cells. All are ciliated and continuous with 

 nerve fibers, which extend toward the brain. Between these 

 olfactory cells are long irregular shaped supporting cells. 

 Whether the difference in shape of the sensory cells is due to 

 difference of function or to mechanical causes was not deter- 

 mined. 



The development of the olfactory nerve and epithelium 

 have been much studied in connection with the problem of 

 metamerism in the vertebate head. Some investigators, with 

 Marshall, consider the olfactory nerve as the first cranial and 

 consequently of segmental value, while others regard it as sim- 

 ilar to the eye in being a modified portion of the brain. 



The recent paper of Disse on the development of the ol- 

 factory nerve and epithelium in the chick is of considerable in 



