22 LABORATORY OUTLINE OF NEUROLOGY 



DESCRIPTION OF FIGURES 4, 5A, AND 5B 



These drawings .illustrating the arrangements of the cranial nerve com- 

 ponents and ganglia of the dogfish were prepared for us by Dr. H. W. Nor- 

 ris and Miss S. P. Hughes, of Grinnell, Iowa. They are based on an inves- 

 tigation of the cranial nerve components of Squalus acanthias by recon- 

 struction from serial microscopic sections. The material used is advanced 

 embryos ("pup" stage), and is probably in all essential respects similar to 

 the adult form. The structures are drawn as seen in flat projection on the 

 median plane and all details shown are drawn true to scale except as noted. 

 The completed research upon which these drawings are based has been 

 published in the Journal of Comparative Neurology, vol. xxxi, 1920, pp. 

 293-402, under the title "The Cranial, Occipital, and Anterior Spinal 

 Nerves of the Dogfish, Squalus acanthias." (This is the article referred to 

 in the text and Bibliography as Norris and Hughes, 1919.) 



FIG. 4. Diagram of the^lateral line canals and their nerves of Squalus 

 acanthias, seen from the side. The ventral portion of the infra-orbital 

 canal is represented as swung ventro-laterally out of its true relation to 

 the other structures. The lateral line canals and their nerves are drawn 

 as they are developed in the advanced embryo (" pup " stage). The exact 

 number of terminal branches of the lateral line nerves supplying the canals 

 is indicated in the drawing. The dots at the ends of the branches indicate 

 the points where they enter the canals. They do not represent separate 

 sense organs within the canals (neuromasts), such as are found in most 

 other fishes. For the form of the sensory epithelium in these canals, see 

 the figures given by Johnson ('17). The ampullae of Lorenzini are not 

 indicated, but a few of the large nerve trunks supplying ampullae ex- 

 clusively are shown (a). 



ABBREVIATIONS 



a, large nerve branches supplying ampullae of Lorenzini only. 



buc. VII, ramus buccalis VII, supplying the greater part of the infra-orbital canal. 



chmd., canalis hyomandibularis, innervated by ramus mandibularis externus VII. 



cinfro., canalis infra-orbitalis, innervated by rami buccalis VII and oticus VII. 



clat., canalis lateralis (main canal of the trunk), innervated by rami supratemporalis 

 X, dorsalis X, and lateralis X. 



cmd., canalis mandibularis, innervated by ramus mandibularis externus VII. 



cspro., canalis supra-orbitalis, innervated by ramuc ophthalmicus superficialis VII. 



cspt., canalis supratemporalis (commissural), innervated by ramus supratemporalis X. 



ct., canalis temporalis (anterior end of main lateral canal), innervated by ramus 

 supratemporalis IX. 



dors.X, ramus dorsalis X, supplying about four end-branches to the main lateral canal 

 of the trunk. 



lat. X, ramus lateralis X (main lateral line nerve of the trunk), supplying the greater 

 part of the lateral canal of the trunk. 



mde. VII, ramus mandibularis externus VII, supplying the hyomandibular and man- 

 dibular canals. 



os. VII, ramus ophthalmicus superficialis VII, supplying the supra-orbital canal. 



ot. VII, ramus oticus VII, supplying about six end-branches to the posterior end of 

 the infra-orbital canal. 



spt. IX, ramus supratemporalis IX, supplying three end-branches in the temporal 

 canal. 



spt. X, ramus supratemporalis X, supplying the supratemporal canal and about six 

 end-branches in the anterior part of the main lateral canal. 



VIII, nervus acusticus. 



