MUSCLE TONUS AND CO2 OUTPUT 



53 



conditions and CO2 determinations were then made. It was 

 found that the animals with blackened eyes respired at a much 

 lower rate than the normal individuals. The varnish of the 

 blackened-eyed animals was next removed and a marked increase 

 in rate of CO2 output resulted. Figure 3 shows graphically the 

 results of such an experiment. 



We may summarize the results of the above experiments by 

 stating that a marked decrease in rate of CO2 output results from 

 a cutting off of the illumination of the eyes and that this effect 

 is a permanent one so long as the eyes are blackened. 



N 'A ■ B 



Fig. 2 Curve showing the effect of blackening the eyes and of the removal of 

 the varnish from the eyes on the rate of CO2 output. Based on average of six 

 individuals. Points on abscissas, N, normal animals; A, animals with eyes 

 blackened; B, animals from whose eyes varnish has been removed. Ordinates 

 same as in figure 1. For further description see text. 



DECAPITATION 



Since it has been pointed out that the brain of insects exerts 

 a marked effect on the tonus of muscles, but does not control the 

 respiratory movements, it was thought that by decapitation a 

 check on the previous results on blackening the eyes could be 

 made. 



Decapitated animals were used three-quarters to one hour after 

 the operations, so that any effects of the operation would not 

 interfere with the experiments. The posture, etc., of the animal 

 after decapitation were much the same as when the eyes were 



