48 JOSEPH HALL BODINE 



laboratory. With this method the CO2 output was ascertained 

 by noting the time required by the animal to produce definite 

 amounts of CO2. In blackening the eyes of the animals asphalt 

 varnish was used. This varnish was found to give off no sub- 

 stances which affected the indicator solution. 



It has been repeatedly pointed out, as the result of experiments 

 to explain the functions of the nervous system of insects, that 

 the brain is the seat of peripheral nerves, the center for inhibiting 

 reflex movements, and for controlling the tonus of the muscles 

 (Bethe^). More recent investigations, and especially those on 

 the functions of the brain of the grasshopper (Ewing^), have 

 definitely shown that the brain controls the tonus of the muscles. 

 It was further shown by this author that neither the supra- 

 oesophageal ganglia or brain of the grasshopper nor the sub- 

 oesophageal gangUon was the center for respiratory movements. 

 Each ganglion of the thoracic and abdominal ventral cord was 

 found to be the center for respiratory movements and reflex 

 actions of the segment and the appendages to which it belonged. 

 It was also pointed out that not only the whole abdomen, but 

 different segments of it continued their respiratory activity when 

 severed from the body. Loeb^ has shown that fight acting on 

 the eyes of an animal produces definite effects upon the tension 

 or tonus of the muscles. Lyon^" and Garrey,^ by blackening 

 both eyes of insects, were also able to show a decrease in the 

 neuromuscular tonus which was normally maintained reflexly by 

 the action of light on the eyes. 



Both the experiments on decapitation and blackening of the 

 eyes have been repeated on grasshoppers by the author, and 

 results which agree with those of the above-mentioned investi- 

 gators have been obtained. It was thought, however, that'some 

 quantitative measure of the effect of light and of the brain on 

 muscle tension or tonus could be gotten by estimations of the 

 CO2 output of the organism. 



