NERVUS TERMINALIS IN DOG AND CAT 151 



connected with the vomeronasal nerves on the one hand and 

 apparently with the forebrain on the other, having thereby the 

 same morphological relations in these mammals as is described 

 for the nervus terminalis of lower forms. Therefore we believe 

 that we are justifieil in considering this nerve the nervus termi- 

 nalis. 



In conclusion it may not be out of place to add a word regard- 

 ing the terminology of this region. One source of confusion in 

 terminology is the use of terms applicable to surface appearances 

 but not applicable to the same structures as they appear in sec- 

 tions made through them. It is still worse when the term used 

 applies to the appearances in some animals but not in others. 

 Manifestly the ideal terminology should express, as far as possi- 

 ble, the function and connections of the parts concerned. Unfor- 

 tunately, however, in some cases we have to apply a terminology 

 before the function and even the connections are known. In 

 the region we have been considering the terms olfactory bulb 

 and olfactory stalk are widely accepted and have been found 

 very convenient in the description of the surface anatomy of these 

 parts. In a previous paper it was suggested in a tentative way 

 that we call the accessory olfactory bulb the 'vomeronasal tuber- 

 cle.' It is true that it forms an elevation on the olfactory bulb 

 of mammals, but in many of the lower forms (reptiles), however, 

 it is described as a pit or fossa. It therefore seems feasible to 

 substitute the term 'formatio vomeronasalis.' This term is con- 

 sistent with 'formatio olfactoria,' the receptive ganglion of the 

 ordinary olfactory nerves, which is in common use. Then if we 

 apply the term 'olfactory bulb' in its true sense to include the 

 entire bulbous enlargement of the olfactory evagination, it will 

 be found composed of four separate and distinct parts: (1) the 

 formatio olfactoria where the ordinary olfactory fibers terminate; 

 (2) the formatio vomeronasalis which is the receptive center for 

 the vomeronasal nerves; (3) the pars bulbaris of the lateral olfac- 

 tory cortex which is to a greater or less extent covered in and 

 attenuated by divisions 1 and 2, and which includes also, the 

 over-lying layer of olfactory tract fibers as well as the deeply 

 placed layer of the pars olfactoria of the anterior commissure; 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 23, NO. 2 



