III. 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 exhibit 

 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 

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

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

 ative Anatomy ('12, p. 167). 



On the structure and functions of the sense organs of fishes 

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

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

 Johnson ('17); Lee ('98); Norris (18); Parker ('03, '03a, '05, 

 '05a, '10, '10a, '11, '12, '12a); Parker and Sheldon ('13); Pea- 

 body ('97); Sheldon ('09b, '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, '15, 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 : dor- 

 sally 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 



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