XIIL] THE FROG. 193 



given off to the posterior parietes of the body, and to the 

 hind-limb. The nerves of the latter are the crural to the 

 front part of the thigh, and the sciatic, which passes to the 

 back of the thigh and ultimately divides into the peronczal 

 and tibial nerves which supply the leg and foot. 



The tenth spinal nerve leaves the neural canal by the 

 coccygeal foramen, and is distributed to the adjacent 

 parts. 



Sympathetic. 



The sympathetic system consists of ten ganglia, connected 

 by longitudinal commissures, and situated on each side of 

 the ventral face of the vertebral column ; in the region of 

 the dorsal aorta they come into close relation with it. Each 

 sympathetic ganglion is joined by a communicating fila- 

 ment with one of the spinal nerves, and the most anterior 

 ganglia are united, in the same way, with the ganglion of 

 the ninth and tenth cerebral nerves. From this a delicate 

 cord, which must be regarded as the most anterior part of 

 the sympathetic, passes into the cranial cavity, on the inner 

 side of the periotic capsule, and unites with the Gasserian 

 ganglion. 



The branches of the sympathetic accompany the vessels, 

 and large branches are given to the viscera of the 

 abdomen. 



The Olfactory organs are two wide sacs which occupy all 

 the space between the mesethmoid cartilage, the antorbital 

 processes, and the premaxillae and maxillae, and open in 

 front and dorsally by the external nares, behind and ven- 

 trally by the posterior nares. The inner faces of these sacs 

 are lined by a very peculiar epithelium, and the olfactory 

 nerves, with some branches of the trigeminal, are distributed 

 to them. 



M. 13 



