HI. DISSECTION OF THE SHARK 



3. This Outline has been prepared for use with either the 

 smooth dogfish, Mustelus canis, or the spiny dogfish, Squalus 

 acanthias. It may be adapted with very slight modifications 

 to the skate or any other elasmobranch. The brains and 

 peripheral nerves of the different sharks, skates, and rays ex- 

 hibit minor differences; but these are not significant for the 

 purposes of this study. 



4. Literature. Laboratory directions for the general dissec- 

 tion of the dogfish are given by Kingsley ('07), Marshall and 

 Hurst ('99), and for the allied skate by T. J. Parker ('00). 

 Good figures of the brain of the shark are found in Parker and 

 HaswelFs Zoology ('10, vol. 2, pp. 158-160), in Wiedersheim's 

 Comparative Anatomy ('07, p. 209) and in Kingsley's Com- 

 parative Anatomy ('17, p. 185). 



On the structure and functions of the sense organs of fishes 

 the following works may be consulted: Bateson ('90); Berger 

 ('82), Ewart ('93); Garman ('88), Herrick ('03, '03a, '08); 

 Johnson ('17) ; Lee ('98) ; Norris and Hughes ('19) ; Parker and 

 others ('03-'18); Peabody ('97); Sheldon ('096, '11). 



5. The chief purpose of the dissection of the fish, as outlined 

 in the following sections, is to secure a clear understanding of 

 the relations between the brain and the other organs of the 

 body. In the fish the brain shows a series of enlargements 

 each of which is directly connected by means of nerves with a 

 particular peripheral organ : the olfactory bulbs with the nose, 

 the optic lobes with the eyes, the acoustic area and cerebellum 

 with the internal ear, the visceral lobe with taste buds, and so 

 on (see Fig. 2 and Herrick, '18, Chap. VII). In the medulla 

 oblongata of this fish there is a series of longitudinal ridges, 

 each of which is connected with a specific type of peripheral 

 end-organs: dorsally is the somatic sensory column, ventrally 

 the somatic motor column, and between these the visceral 

 sensory and motor columns. Here are located the cerebral 

 centers of important reflex systems (see Figs. 2 and 6, Section 



16 



