OP SENSATION AND THE SENSES. 477 



also lived four days without its head, and even evacuated excrement 

 during this period, but it could no longer move its wings, and was 

 sensible only to pressure made at its caudal extremity. Treviranus 

 also cites an experiment of Walckenaer, in which Cerceris ornata had 

 its head cut off just as it was entering the cells of Halictus lerebrator, 

 when it still continued its endeavours, and even turned round towards 

 the hole upon being placed in a contrary direction. 



274. 



To endeavour to harmonise these discordant results^ or rather, to 

 ascertain to which the preference was truly to be given, I myself insti- 

 tuted the series of experiments which follow. 



Among the Coleoptera it was chiefly the water-beetles, viz. Dyticus 

 fiulcatus and cinereus, which I made use of. I first took the male D. 

 cinereus, and cut off its head, but the crop and proventriculus were also 

 thereby removed from the body ; from the very instant it totally ceased 

 all voluntary motion, but upon pinching the feet severely with a pair 

 of pliers a strong reaction of the muscular irritability was produced ; 

 the posterior legs immediately made three or four swimming motions, 

 but they then remained in their preceding lifeless and gently bent 

 position. This reaction continued, but constantly decreasing in force, 

 for about half an hour, after which the severest pinching was not able 

 to produce it. 



I opened the breast of a lively female Dyticus sulcalus, between the 

 second and third pairs of legs, so that the nervous cord was laid bare. 

 With a pair of pliers I now laid hold of the nervous cord, and removed 

 it ; the left posterior leg was immediately lamed, but the right one 

 and all the four anterior legs still exercised their voluntary motions, 

 and the creature could still tolerably swim when thrown into the 

 water. When placed upon its back, the contractions of the muscles 

 were distinctly seen. These continued for about an hour, the posterior 

 legs then lost all motion, and even their irritability, whilst the anterior 

 ones still possessed it, but yet a decrease of animation was clearly seen, 

 and in about three hours afterwards it was completely dead. 



In another male Dylicns sulcalus I separated the nervous cord close to 

 the soft connecting membrane between the pro- and meso-thorax ; in 

 the course of a few seconds the motion of the four posterior legs ceased, 

 whilst the anterior ones retained their perfect mobility, but signs of 

 irritability still presented themselves. The anterior legs, even after 



