Olfactory Apparatus in Dog, Cat and Man 41 



Histology of the Organon Yomeronasale. 



Fig. 18 is a transection of the head of an embryo kitten in the region 

 of Jacobson's organ. This shows the position of the organ, the car- 

 tilaginous capsule and the thickness of the epithelium. Figs. 54 and 55 

 will show the complete and partial capsule in the kitten. The fine 

 structure is described by several investigators. I have been chiefly 

 concerned with the sensory cells. In the kitten (Figs. 54a^ 55a) sense 

 cells were found. These agreed in every way with the olfactory cells 

 of the nasal mucosa. There are two processes : the thicker, peripheral 

 one, and the fine, somewhat varicose, central fiber. The axone was 

 followed for a considerable distance in the submucosa. No olfactory 

 hairs were found, but in Fig. 54a indications of these are seen in the 

 spike-like process. 



I have no hesitation in calling these sense cells nerve cells, apparently 

 identical with those of the olfactory mucosa. Free terminations men- 

 tioned by von Lenhossek, 1892, and Cajal, 1894, were not found, but 

 we should consider those, from the gross dissection, to be the endings 

 of the 5th nerve, as several branches of this nerve were traced into the 

 organ. I believe, then, with others, that the vomeronasal organ is 

 intimately connected with the olfactory sense. 



Eesults. 

 dog and cat. 



1. The olfactory nerves are large and numerous in the dog and the 

 cat, relatively less in the cat. 



2. About one-half of the ethmo-turbinal folds are olfactory. This is 

 a large distribution as compared with man. 



3. All the folds of mucosa adjoining the cribriform plate are olfactory. 



4. The mucosa is thick in the olfactory region; thin beyond this; the 

 transition is sharply marked. 



5. The mucosa of the septum is in two parts. The upper part is lined 

 by the dorsal turbinated folds; the lower part is lined by a continuation 

 of the mucosa of the cephalic part of the nose. About one-third to one- 

 half is olfactory. 



6. The anterior ethmoidal nerve innervates the olfactory folds and 

 septum ; its branches extend from the cribriform plate to the tip of the 

 nose ; it also innervates the roof and upper lateral Avail of the nose. 

 Small branches pass among the olfactory folds. 



