EWING : OBSERVATIONS ON ACRIDID^. 307 



oesophageal ganglion or brain proper, and a double chain of 

 ganglia on the ventral side of the body, composed of one snb- 

 oesophageal, three thoracic and five or six abdominal ganglia 

 connected by a double nerve fibre with each other and with 

 the brain. Each ganglion consists of two halves intimately 

 united by a transverse commissure. 



The experiments, in the course of which the following notes 

 were made, consisted in removing or severing, by means of fine, 

 sharp, curved or straight scalpels or scissors and hooked for- 

 ceps, different parts of the nervous system of the insect. The 

 nervous system had been carefully studied and outlined in re- 

 lation to definite landmarks on the exterior of the body. During 

 the operation the animal was held in an insect holder, while 

 the parts of the nervous system were exposed and removed 

 with aseptic precautions. The regions from which parts were 

 removed were examined under the microscope, to ascertain 

 whether more or less of the planned lesion had been executed. 

 The chitinous piece was replaced then over the wound and held 

 in place by shellac or wax cement. The insects were kept 

 under fairly constant external conditions throughout the period 

 of observation. A post-mortem was made in most cases. 



My work was pursued under the supervision of Professor 

 Hyde, of the physiological department, to whom I am indebted 

 for much valuable assistance. 



I. Extirpation of the Brain. 



The rate of the respiratory movements was slowed, otherwise 

 this operation has no marked effect upon respiration. Pinch- 

 ing the antennae, which, after the brain is removed, remain mo- 

 tionless in any position in which they are placed, produced no 

 reflex movements. There are evidently no sensations left in 

 these organs, although the grasshopper would still stroke them 

 with his front feet, as the normal animal occasionally does to 

 clean them. Bethe observed this action and thinks that in the 

 operation a stimulus is aroused in the inferior cesophageal 

 ganglion that is similar to a stimulus produced by the antennae 

 in the intact animal. The head is lowered sideways, the fore 

 leg is stretched toward the region where the antenna is nor- 

 mally found. Contact with the antenna causes the foot reflexly 

 to take an increased hold on it and to press it to the ground, 

 as if to prevent the escape of the seemingly foreign body. The 



