586 CEPHALOPODA. 



aspect of the ganglionic collar, a pair of nerves (7), each of which soon 

 dilates into a large ganglion (s), from whence are derived the nerves of 

 the internal labial tentacles (9) and also other gangliform nerves (10), 

 distributed to what Professor Owen regards as the olfactory apparatus ; 

 lastly, the anterior collar gives off nerves (ll) which penetrate the mus- 

 cular integument and supply the infundibulum. 



(1570.) In the Dibranchiate Cephalopods, the nerves derived from 

 that portion of the brain that may be regarded as analogous to the 

 anterior collar of Nautilus supply the locomotive sucker-bearing arms, 

 the labial apparatus, and also the auditory organs (fig. 294, c, d) ; but 

 the latter have not been found to exist in Nautilus Pompilius. 



(1571.) There is no possibility of doubting that the above nerves, 

 distributed as they are to the complex sensitive tentacula connected 

 with the head and parts of the mouth, represent the fifth pair in the 

 Vertebrata their general distribution and semi-ganglionic character 

 being, cceteris paribus, precisely similar ; so that those portions of the 

 brain of vertebrate animals from whence the trifacial and auditory 

 nerves originate may reasonably be compared with the anterior sub- 

 oesophageal collar of the Cephalopoda. 



(1572.) The posterior suboasophageal ganglionic ring (fig. 291, 4) 

 may be compared to the medulla oblongata of quadrupeds. In Nauti- 

 lus it gives origin, 1st, to numerous nerves (13) which, after a short 

 course, plunge into the muscular parietes of the body, to which they are 

 distributed ; 2ndly, to two large cords (14) which terminate by be- 

 coming gangliform (16), and supply the branchial apparatus and the 

 viscera thus representing the par vagum in their distribution, and in 

 like manner communicating with branches apparently corresponding 

 with the sympathetic nerves that are spread out over the heart and 

 ramifications of the vascular system ; lastly, slender nerves, allied to the 

 sympathetic, accompany the vena cava into the abdomen. 



(1573.) Such being the arrangement of the principal nervous ganglia 

 and the general distribution of the nerves, we must now turn our atten- 

 tion to the instruments of sensation possessed by these comparatively 

 highly-gifted animals ; and these, as we shall soon perceive, are in all 

 respects correspondent, in the perfection of their structure, with the 

 exalted condition of the brain, and, from their peculiar organization, 

 highly interesting to the physiologist. 



(1574.) The sense of touch, as might naturally be expected, resides 

 principally in the tentacula, or feet, as they are generally termed, placed 

 around the mouth, and forming, as we have already seen, instruments 

 of locomotion as well as prehensile organs. In the Dibranchiate Cepha- 

 lopods these tentacula are armed with the tenacious suckers described 

 in a former page ; but in the Nautilus they are so peculiar, both in 

 structure and office, that a more elaborate description of them becomes 

 requisite in this place, for which, of course, we are necessarily indebted 



