480 PHYSIOLOGY. 



mouth. These caterings continued for a quarter of an hour, but the 

 body was entirely dead. 



In another lively Eristalis nemorum I made an incision transversely 

 through the eyes, and seriously injured the brain ; the insect, however, 

 still retained the perfect mobility of all its legs, and crept about, although 

 but slowly; shortly, however, its strength decreased, it reposed quietly, 

 and but slightly moved upon excitement ; in an hour it was quite dead, 

 but still displayed slight irritability of the muscles upon violent external 

 excitement. 



275. 



From these experiments, and those communicated by Rengger, we 

 may deduce the conclusion, that after the separation of the nervous 

 cord at any part, the voluntary motion of the organs seated beyond the 

 point of incision is lost, but that the irritability of the muscles, that is 

 to say, their power of re-action upon external excitement, is retained 

 by these organs as long as life is still present, but that it disappears 

 with it. It thence consequently follows that the nerve passing to the 

 muscle supplies the place of external excitement, and that therefore 

 the will can act upon the muscles only through the medium of the 

 nervous system. These experiments also confirm the assertion so fre- 

 quently repeated, that the brain is the principal of all the ganglia, and 

 that the causes of all the vital phenomena exist in it, and proceed from 

 it. The instance in which the male Dyticussw&m about a considerable 

 time after the removal of its brain appears to contradict this conclusion, 

 but I am still very strongly inclined to perceive nothing but irrita- 

 bility in the rowing of the feet. The entire uniformity of the motion 

 speaks strongly in favour of this opinion, as well as the circumstance 

 likewise that the beetle deprived of its brain did not execute these 

 motions so long as it lay upon its belly on a dry surface. We may also 

 deduce from these experiments, that still for a short time after the 

 removal of the brain, not merely signs of life but even proofs of 

 voluntary motion present themselves, which are the stronger the 

 more imperfect the injury to the brain may be. We may here class 

 also the experiments made by Treviranus, but I doubt their entire 

 accuracy. How could a beetle seek ways to escape when all the 

 organs whereby it might perceive such opportunities were removed from 

 it.'' Walckenaer's observation is more probable, that the Cerccris 

 repeated sewral times its preceding endeavours after the loss of its 



