NERVUS TERMINALIS IN REPTILES AND MAMMALS ^ 



J. B. JOHNSTON 



From the Institute of Anatomy, University of Minnesota 



TWELVE FIGURES 



The table on the following pages will show in the briefest form 

 the occurrence and relations of the nervus terminalis in various 

 vertebrates. 



In all the forms in which the nerve enters the olfactory bulb 

 it has been shown that its fibers pierce the formatio olfactoria 

 to pass on to their proper endings in some part of the forebrain. 

 Where the nerve is described as entering the brain near the pre- 

 optic recess it is quite probable that the point of entrance is 

 near the neuroporic recess as in selachians. In both cases at 

 any rate the root has its attachment to the brain beside the 

 lamina terminalis. From these facts it appears that the nervus 

 terminalis in most fishes and amphibians is a ganglionated nerve 

 whose root enters the forebrain caudal to the olfactory bulb, 

 usually near the site of the embryonic neuropore, and whose 

 fibers are distributed to the wall of the nasal sac. The presence 

 of bipolar ganglion cells in the course of the nerve shows that 

 it is in part at least a receptive nerve. Whether there are also 

 efferent fibers of the sympathetic type (vaso-motor) or other 

 components in the nerve can not be determined at present. 



The purpose of this paper is to give a general description of 

 the nerve as it appears in certain reptilian and mammalian 

 embryos. I wish to acknowledge my great obligation to Dr. G. 

 Carl Huber who has kindly given me the free use of his excellent 

 collection of human and other embryos. The embryos studied in 

 his laboratory are indicated below. 



1 Neurological Studies from the Institute of Anatomy, University of Minne- 

 sota, No. 17. 



97 



