360 



LECTURE XVI. 



that they found in the works of Lyonnet corroboration of this incon- 

 clusive physiological view. Lyonnet, however, expressly denies that 

 the parts which he called brain and spinal marrow in the insect were 

 similar in anatomical structure to those in the higher animals. 



" The spinal marrow of the ca- 146 



terpillar, if one may say that it 

 possesses such," observes Lyon- 

 net, " sensibly differs from that 

 of man. It is slender ; it bifur- 

 cates at intervals, and enlarges 

 from distance to distance to form 

 its masses, which I have named 

 ganglions." The intervening 

 chords Lyonnet terms "conduits 

 de la Moelle epiniere." He par- 

 ticularly points out the difference 

 in relative position, and in the 

 means of protection assigned to 

 the ganglionic columns in insects, 

 and to the spinal chord in the 

 higher animals. As to any views 

 of distinct physiological proper- 

 ties in the ganglions or the non- 

 ganglionic nervous tracts, none 

 such appear in the works of 

 Lyonnet ; nor, indeed, did they 

 form part of the domain of phy- 

 siology at that period ; and it 

 was a great advantage to Zootomy 

 that Lyonnet looked at his sub- 

 ject with the eye of truth, and 

 not through the prism of any pre-formed physiological notions. 



The super-cesophageal ganglion gives off ten nerves ; eight in pairs, 

 and two solitary or azygos nerves ; one of these latter is the anterior 

 oesophageal ring (^fig. 146, e). Its extremities are connected with 

 the cephalic ganglion immediately anterior to the attachment of the 

 principal columns which form the posterior oesophageal ring. The 

 second solitary nerve (c) is sent off from the middle of the posterior 

 side of the cerebral ganglion, and proceeds backwards to the oeso- 

 phngus. The cephalic nerves, sent off in paii*s (b, b), supply the 

 anlennfe, the ocelli, the muscular and integumentary parts of the 

 head, and communicate with branches of the maxillary nerves. The 

 most remarkable pair, however, is that which arises anterior to the 



Immediately after 

 changing to a pupa. 



^F 



Full-grown 

 Larva. 



Half an hour 



before 



changing. 



Vanessa urticse. 



