THE FHix; 



PLATE V. 



THE FROG. THE NERVOUS SYSTEM AND BRAIN, THE ANATOMY OF THE OLFACTORY, 



VISUAL, AND AUDITORY ORGANS. 



FIG. I. The cerebro-spinal axis and the course of the fifth cranial nerve, displayed 

 from above. 



The whole dorsal integument was removed, and the neural cavity opened up from 

 above ; on Ihe right side the nasal bone has been removed, and the eye dissected out. x 2. 



FIG. II. The cerebro-spiual axis, with the great nerve trunks including the sympa- 

 theticdissected from the ventral aspect. The origins of all the cranial nerves except the 

 iv* are shown, and the sympathetic is indicated on one side for its whole length. 



The entire ventral body-wall, together with the viscera and the floor of the mouth, were 

 removed. After carefully dissecting the aorta away from the sympathetic, that system was 

 removed on the left side. The whole neural canal was next laid open, by removal of the 

 vertebral centra and the floor of the skull ; the eye on the left side, the hinder portion of the 

 upper jaw on the right, and the floor of the auditory capsules of both sides, were dissected 

 away. The vn cranial, i spinal, and sympathetic nerves are all shaded darkly, x 2. 



FIG. III. The cranial nerves, irrespective of those connected with the olfactory, 

 visual, and auditory organs, together with the first five spinal nerves, and sufficient of the 

 sympathetic to show the origin of the splanchnic nerve. 



The whole integument covering the head was removed, together with the eye and 

 hinder portion of the upper jaw with its associated parts ; the left arm and shoulder-girdle 

 were also removed. The body-cavity and the cisterna-magna were both opened up and the 

 spinal nerves n to v turned forwards, to render clear the relations of the sympathetic. 

 The vn cranial and sympathetic nerves are tinted as in Fig. II., and all the spinal nerves 

 are drawn in black, x 2. 



FIG. IV. The leading nerves of the hind limb, seen from the dorsal aspect. 



The gastrocnemius, peroneus, and tibialis-anticus muscles have each been reflected, and 

 those of the upper segment of the limb pulled apart, sufficiently to display the nerves 

 drawn. Nat. size'. 



FIG. V. A transverse section, taken immediately behind the exit of the second spinal 

 nerve, to show the relations of the nerve roots and investing membranes, x 6. 



FIG. VI. The brain, seen from above in situ, before the removal of the pia mater. 



* This is shown in Fig, VIII, 



