162 STUDIES ON RESPIRATION. XIX 



The interpretation of these results raises several questions. For 

 example, which part of the curve represents stimulation, which anes- 

 thesia, and at what point do the toxic (irreversible) changes begin? 

 In regard to the latter, it was found that, even when the respiration 

 had been reduced below normal, complete recovery was possible on 

 removal to distilled water, provided that the depression was not too 

 great (Fig. 2). Below a certain range the respiration fell even more 

 rapidly when the seeds were removed from the ether. There was no 

 evidence of incomplete or partial recovery.^ It is thus seen that up 

 to a certain point, which may be below the normal rate of respiration, 

 the curve represents changes in the rate of carbon dioxide production 

 which are completely reversible. The boundaries of the stimulatory 

 and anesthetic effects must be left for future experiments to decide. 



SUMMARY. 



Using these concentrations of ether (1 per cent, 3.65 per cent, 7.3 

 per cent), the following conclusions may be drawn. 



1. The first effect of ether is to cause a depression in the rate of 

 respiration. This is followed by a rapid rise above normal, which in 

 turn is succeeded by a fall. 



2. With all these concentrations the respiration is ultimately re- 

 duced to approximately the same level; the stronger the ether, the 

 less time required to produce this result. 



3. Even when the respiration has been reduced below normal, 

 recovery is possible on removal from the ether, and appears to be 

 complete, if sufficient time is allowed. If, however, the rate has 

 been too far depressed, no recovery is possible. 



4. These results extend those of Irwin on frog eggs and Fundulus 

 embryos. 



* These experiments were made by Osterhout's method.' 



