MR. NEWPORT ON THE NERVOUS SYSTEM OF THE SPHINX LIGUSTRI. 407 



close apposition until they arrive at a ganglion. The motor then becomes more di- 

 stinct, and passes over the ganglion without uniting with it, and immediately after- 

 wards is again closely approximated to the sensitive. A distinct line between the two 

 tracts extends along the whole lateral surface of each cord, and is more or less evident 

 in different parts of its course. It will thus be seen that the ganglia are situated al- 

 most entirely along the under surface of the cords, and it is from these that the sensi- 

 tive* portion of the double or symmetrical nerves (o, o, o, o, o,) of the body take their 

 origin. The manner in which the nerves from the motor tract unite with those from 

 the ganglia of the sensitive in the Lobster, to form these symmetrical nerves, is not 

 at first very apparent. Upon close examination it seems to be by fibres coming off 

 laterally from the motor tract, just above the anterior margin of each ganglion, pass- 

 ing backwards and outwards, and immediately uniting with those from the ganglion 

 into distinct trunks. The ganglia in the thorax are rounder, larger, and closer 

 together than the caudal or post-abdominal ones, and give nerves to the true organs 

 of motion, the legs ; to the claws, mandibles, and feelers ; to the glandular structures, 

 and the circulatory vessels in the branchiae and thorax. The caudal ganglia are of 

 a much smaller size, and are of an oval shape. Each of these gives off two pairs of 

 nerves (o, o), which again divide into two branches, and pass outwards close to the 

 under surface of the body, supplying the large trunks of circulatory vessels which 

 pass along the same course with them, and the external layer of muscles. The pos- 

 teiior division of the second pair from each ganglion is larger than the others, in con- 

 sequence of its again dividing into two branches as soon as it reaches the lateral 

 margin of the body. The largest of these branches (/?, p) descends to supply the 

 muscles of the false feet, the other ascends to those of the lateral surface of the seg- 

 ments. This is analogous to the means by which the false feet are supplied in the 

 larva of Sphinx Ugustri, and other Lepidopterous insects, in all of which they 

 are supplied from the ganglia in the abdominal region, which are analogous to the 

 post-abdominal of the Lobster. The terminal ganglion [Plate XVIL fig. 40. (14.)] is 

 the largest, and gives off four pairs of large nerves, and, as in insects, was originally 

 formed of two ganglia. The two terminal nerves (s) from this ganglion, which has 

 coalesced longitudinally, pass on each side the rectum, and divide each into two 

 branches. The terminal branch supplies, and is entirely lost, in the rectum and 

 sphincter ani, and the other supplies the muscles which elevate and expand the anus 



* While engaged upon the anatomy of the Lobster I obtained a large living specimen, which, although ap- 

 parently vigorous and healthy, appeared to suflFer but very little pain when pricked or pinched, and was of a 

 much lighter colour than usual, its whole covering being quite blue, instead of the usual blackish purple. 

 Upon killing the animal and examining its spinal cords, the motor columns and nerves were of the usual size 

 and appearance, but all the ganglia of the sensitive columns, particularly those in the post-abdominal region, 

 were exceedingly small, and each inclosed only a very small nodule of grey matter. May we not infer from 

 this fact, that the degree of sensation in the nerves belonging to the spinal column very much depends upon 

 the size of the ganglia and the quantity of grey matter they contain ? , 



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