4J8 PHYSIOLOGY. 



four hours, still exercised their voluntary motions, although with less 

 vivacity, but in the evening the insect was dead. 



In a fourth perfectly animated male Dyticus sulcattts, by an incision 

 which removed the horny integument of the head, I laid the brain bare. 

 Immediately much yellowish brown green blood streamed forth ; it was 

 perfectly clear and viscid, and covered the entire wound, and stood 

 upon the naked part like a drop of water. I thus allowed the insect to 

 go ; it retained its complete motion, but moved all its limbs slowly and 

 convulsively as if severely injured. I now removed the brain by means 

 of pliers ; the insect immediately became motionless as dead, and did 

 not move a single joint as long as it lay upon its belly. Upon my 

 teasing it, after about a minute it endeavoured to cling with its legs, 

 but this motion appeared to proceed rather from the. irritability of the 

 muscles than from its own volition. I now laid it upon its back, and 

 it directly made its usual swimming motions, during which, as when 

 swimming, the anterior pair were drawn closely up to the breast. These 

 motions lasted uninterruptedly as long as the insect lay upon its back ; 

 if I laid it upon its belly they ceased, and the insect again moved no 

 limb. I now cast it into the water, when it swam upon the surface 

 with the greatest rapidity, impelled by incessant natatory strokes, 

 striking all its comrades that it met on one side by the violence of its 

 motions, and continued thus uninterruptedly for about half an hour. 

 It did not, however, descend to the bottom, nor did I see any respiratory 

 action in its abdomen. After this, upon the gradual decrease of the 

 force of its strokes, it lay upon the surface with distended legs, but 

 displayed irritability upon the legs being pinched ; lastly, towards 

 evening, the experiment having been made about 1 1 a. m., all life had 

 vanished. 



The brain was similarly laid bare in a female Dyticus sulcatus, but 

 the incision passed obliquely through the right eye, and wounded its 

 right hemisphere, whereby the insect lost the voluntary motion of the 

 left posterior foot. I now removed the brain entirely, and the insect 

 became instantly lifeless, but in the course of a few seconds the legs 

 recovered their motion, but not to the same extent as in the preceding 

 experiment. Cast into the water, this female did not swim like the 

 former insect, but lay with extended legs, moving with a catch some of 

 its joints ; these motions could be perceived, even after an hour, upon 

 effective excitement, but towards evening, as in the preceding experi- 

 ment, the beetle was perfectly dead. 



