296 H. W. NORMS AND SALLY P. HUGHES 



friend rather than an agent. For the loan of literature and the 

 freedom of access to his private library the writers are under 

 lasting obligation to Prof. J. S. Kingsley, of the University of 

 Illinois. 



Acknowledgment is made of a grant from the Bache Fund of the 

 National Academy of Sciences, which has made possible the early 

 completion of this research. 



MATERIAL AND METHODS 



Heads of Squalus acanthias and of Mustelus californicus, in 

 the 'pup' stage, were fixed in vom Rath's picric-acetic-osmic- 

 platinic mixture and sectioned by the celloidin method. The 

 best results were obtained by fixing in a 10 per cent solution of 

 neutral formalin, followed, after thorough washing, by the vom 

 Rath treatment. Where the latter is applied to fresh material 

 (dogfish), many kinds of structures are blackened; but when 

 preceded by formalin fixation, only nerves and muscles are thus 

 affected and stand out distinctly, on a nearly -colorless background. 

 Material long preserved in formalin does not seem to react as 

 favorably as that which has been recently fixed. The sections 

 were cut 15/x and 20/x thick, mounted in balsam on lantern-slide 

 covers, and covered with large sheets of mica. In most instances 

 the sections were counterstained on the slide in Van Gieson's 

 picrofuchsin. By this treatment the most faintly stained nerve 

 fibers could be distinguished readily from connective tissue. Pro- 

 jections of the nerves were made upon the sagittal and horizontal 

 planes. A wax model was made of one half of the medulla 

 oblongata, especial attention being given to an analysis of the 

 ganglia. A model of some of the structures found in the orbit 

 has served to make clear some of the relations of the ciliary 

 ganglia. 



THE OLFACTORY NERVE 



The writers see no good reason for disagreeing with Brookover 

 ('10, '11, '14, '15) in the opinion that the nervus terminalis is 

 in origin and structure related to and a part of the olfactory 

 nerve. Belogolowy ('11), from his researches upon the develop- 



