306 



KANSAS UNIVERSITY SCIENCE BULLETIN. 



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/'sT 



directly from the spiracles. In addition 

 to these superficial air-sacs there are very 

 many, probably several hundred, distri- 

 buted throughout all parts of the body. 

 Of the tracheal tubes there are two main 

 trunks on each side. One is placed above 

 and the other below the plane of the ali- 

 mentary canal. They communicate with 

 each other and with the air-sacs and spir- 

 acles. Besides these large trunks there 

 are countless ramifications to all parts of 

 the body, communicating by their finest 

 twigs with internal cells. The oxygen of 

 the air is thus separated from the fluids 

 of the body by a very delicate endothelial 

 membrane. 



The respiratory movements in the nor- 

 mal grasshopper consist of an expiratory 

 and an inspiratory phase. During in- 

 spiration the active contraction of the 

 abdominal muscles produces an increase 

 in the breathing space, in that the antero- 

 posterior and dorso-ventral diameters of 

 the abdomen are increased, and air passes 

 in through the open spiracles to fill the 

 air-sacs, since the pressure within, in con- 

 sequence of the formation of a partial 

 vacuum, becomes less than atmospheric. 

 In active or forced inspiration, the abdo- 

 men may be elongated, and by a forward 

 and backward movement of the head, the air-spaces in the 

 abdomen may be still further increased. Expiration is a passive 

 movement ; that is, the muscles relax and the breathing space 

 is decreased as the abodmen relaxes by its own elasticity. At 

 the same time the return of the abdominal segments to closer 

 <^ontact with each other, forces the contents of the air-sacs along 

 the tracheal tubes into their finer ramifications, and also expels 

 air that has been in contact with the fluids of the body into the 

 air-sacs and thus to the exterior of the body. 



The nervous system of the grasshopper consists of a supra- 



i 



V 



— a. 



- a. 



~~a 



~~A 



-A 



Nervous System of the 

 Grasshopper. 



Diagratnatic. 



a. Abdominal Ganglia. 



d. Infra-CBsophageal 

 Ganglion. 



b. Supra-cesophageal 



Ganglion or Brain. 



c. Thoracic Ganglia. 



