136 THE NERVOUS SYSTEM [CH. VI 



observers, that the terminal segments of the abdomen of a large 

 Aeschnine Dragonfly may be snipped off with scissors and offered 

 to the head, which will proceed to devour them with apparent 

 relish. This points in the same direction, while it also emphasizes 

 the independence of the ventral ganglia. 



4. The effect of mutilation, shock, decapitation, etc., on 

 respiratory movements has been studied in detail by Barlow [6]. 

 The results shew that numerous external influences affect the 

 rate and power of the respiratory movements ; that the respiratory 

 movements of each abdominal segment are to some extent inde- 

 pendent of the rest, provided the ganglia are not damaged ; that 

 decapitation does not stop these movements, but diminishes their 

 frequency and force ; and, finally, that even severe shock, though 

 it may stop them for a time, cannot prevent a feeble revival of 

 them later on. 



It seems quite clear that much more remains to be done in 

 the way of devising interesting experiments on this subject, and 

 that there is still a great deal that we do not understand in the 

 working of the very peculiar nervous system of the Dragonfly. 



