LECTURE VI. ^63 



one to supply the viscera and the rest of 

 the body. Mr. Hunter says in his MS.> 

 " There are two large nerves descending on 

 either side of the oesophagus, and then 

 uniting into one, forming a ganglion at 

 their union, which he thinks serves the 

 office of the sympathetic or visceral nerve, 

 and the medulla spinalis/' 



In fish and reptiles, the nervous system 

 approximates to that which is found in the 

 higher classes of aninals. In the former, 

 it is extremely small The brain and me- 

 dulla spinalis of the squalus maximus is 

 exhibited in the Museum. It therefore 

 appears that fish, such agile, powerful, in- 

 defatigable creatures, which are also so sur- 

 prizingly retentive of life, have not only 

 a very languid circulation, scanty respi- 

 ratory process, but also a disproportionately 

 small nervous system. We need not in- 

 deed marvel at such facts, because the ani- 

 mals in which the energies of life seem 

 greatest, are those in which neither circu- 

 lating organs nor nerves are discoverable. 



s 4 



