220 JOSEPHINE ALBERTA WILLIS. 



or giving out of oxygen is found to occur within the first 30 

 minutes of exposure to the gases, but as the period of exposure 

 increases, the gas is reabsorbed. 



DISCUSSION. 



Respiration in insects depends upon the supply of air in the 

 system of tracheae or tubes ramifying through the body. Equili- 

 brium is maintained by muscular movements of the abdomen as 

 well as by diffusion of gases and, for this purpose, eight separate 

 segments of the abdomen, on either side in a ventro-lateral 

 position, bear a spiracle or small tracheal opening through which 

 the air in the tubes is periodically changed. 



The relation between the respiratory and circulatory systems 

 of insects differs from that of the vertebrates and is of such an 

 arrangement that the blood seems to have little to do with the 

 transportation of oxygen and carbon dioxide except in a purely 

 mechanical way. In the grasshopper, the body fluid is kept 

 circulating by means of a tubular heart lying along the dorsal 

 side of the body cavity and as there are no blood vessels, the fluid 

 directly bathes the tissues. Thus, it is by means of the minute 

 tracheal vessels of the respiratory system that the gases are 

 carried into the body and diffuse through the delicate tracheal 

 membranes into the blood and tissue cells. 



In a qualitative work on the influence of gases on the respiratory 

 movements of grasshoppers, Walling (2) found that hydrogen 

 inhibits the respiratory movements, then the animal partially 

 revives and will continue to live in the hydrogen atmosphere for 

 as long as four days. In oxygen the animal may be either active 

 or dormant, depending upon the individual and. finally, dies 

 from lack of food. Carbon monoxide reacts similarly to carbon 

 dioxide and the animal will recover after longer exposures to the 

 gas. As for carbon dioxide she found respiratory movements to 

 cease within twenty to thirty seconds, but they returned when 

 the animals were removed to fresh air. They could endure long 

 exposures. 



The characteristic behavior exhibited by the animals in the 

 present experiments under the influence of carbon dioxide is 

 perhaps due to physical changes in the tissue cells. It is known 

 that carbon dioxide and oxygen may exist in solution in their body 



