22 LABORATORY OUTLINE OP 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 Miss S. P. 

 Hughes under the direction of Dr. H. W. Norris, of Grinnell, Iowa. They 

 are based on an unpublished investigation of the cranial nerve components 

 of i-'qualus acanthias by reconstruction from 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. It is expected that the complete research 

 upon which these drawings are based will be published in the Journal of 

 Comparative Neurology during the year 191S. We are greatly indebted 

 to Dr. Norris and Miss Hughes for the privilege of using these data in 

 advance of the publication of their paper. 



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. 



clot., 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 ramus ophthalmicus superficialis VII. 



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



cU, canalis temporalis (anterior end of main lateral canal), innervated by ramus supratem- 

 poralis IX. 



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

 the trunk (contains also a general cutaneous element, ramus auricularis X, see Fig. 5A) . 



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 mandibular 

 canals. 



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



ol. 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. 



