108 J. B. JOHNSTON 



clearly a ganglionated nerve connected with the neuroporic region 

 of the forebrain and supplying free nerve endings to the vomero- 

 nasal organ and probably to a variable part of the nasal sac. 

 The olfactory fibers arising in the vomero-nasal organ run in the 

 same bundles with the nervus terminalis, but enter the bulbus 

 olfactorius. 



The existence of this nerve in adult fishes and amphibians and 

 in embryonic reptiles and mammals warrants a careful search for 

 it in adult reptiles and mammals. Already McCotter ('12) has 

 found strands connected with the vomero-nasal nerve in the adult 

 dog which enter the brain in the proper position for the nervus 

 terminalis. Further studies may show this nerve present in adult 

 turtles and snakes and in various mammals. It is probable that 

 this region of the adult human brain has never been studied in 

 any way that is favorable to the discovery of this nerve if it 

 should be present. 



Discussion of either the morphological or physiological signifi- 

 cance of the ner\iis terminalis would not be profitable at this 

 time. It is clear that there exists in the most anterior vertebrate 

 segment a receptive nerve in addition to the olfactory. The 

 olfactory and the ner\Tis terminalis may be regarded as two 

 components of a segmental nerve, analogous to the gustatory and 

 general cutaneous components which exist together in the VII or 

 the IX cranial nerves in some fishes. That the olfactory nerve 

 and nervus terminalis have come to have separate roots and 

 very widely differentiated centers is no bar to this view. For the 

 two components in the VII or IX, or in any nerve, have differ- 

 entiated centers and in many cases the fibers of one component 

 in a cranial nerve become segregated at their entrance into the 

 brain so as to form one or more pure rootlets. It is possible that 

 the nervus terminalis contains one or more other components 

 still. Brookover's work on Amia seems to show that this nerve 

 has a relation with the head sympathetic and that the larger 

 part of the cells in its course are sympathetic cells concerned 

 probably in vaso-motor functions. About forty fibers constitute 

 the forebrain root of the ganglion terminale. These Brookover 

 would regard as preganglionic sympathetic fibers. This inter- 

 pretation would not be tenable if these fibers are the axones of 



