216 STUDIES ON RESPIRATION. V 



eggs which might correspond to the peehng of the epidermis in case 

 of the tadpoles, but owing to the presence of ciha, the decrease in CO2 

 output may be partly influenced by the cessation of ciliary move- 

 ment as result of anesthesia. 



Fundulus heteroditus. 



In order to understand the true nature of the effect of the production 

 of CO2 by animals it was necessary to avoid completely the disturb- 

 ances due to ciliary and muscular movement, and to peeling of the 

 skin. The embryos of the fish, Fundulus heteroditus, 2 days old, 

 were chosen for this purpose; at this stage of embryonic develop- 

 ment there are no muscles, no cilia, and no skin, and furthermore 

 the heart beat has not yet commenced. 1 day before the experi- 

 ment was carried out, the jelly surrounding the membrane was 

 removed, so that the embryos would not adhere to each other during 

 the course of experimentation. 



Fig. 5, Curve A, shows the effect of 0.73 per cent ether solution on 

 the CO2 production- of the fish embryos. A gradual decrease takes 

 place to about 46 per cent of the normal, after which the rate remains 

 almost constant during the rest of the experiment. Fig. 5, Curve B, 

 shows the effect of 3.65 per cent ether solution. There is a slight de- 

 crease at first, which is followed by an increase of carbon dioxide; this 

 is succeeded by a decrease. Curve C shows the effect of 5.48 per cent 

 ether; a tremendous increase of the carbon dioxide output takes 

 place. If there is any decrease at the start it must be so brief as 

 to escape observation. The rate soon reaches a maximum, after 

 which it falls rapidly. 



During the increase in 3.65 per cent and 5.48 per cent ether the 

 embryo becomes gradually more opaque ; this process begins to be ob- 

 servable after 20 minutes in 3.65 per cent ether and after 4 minutes 

 in 5.48 per cent ether. 



These experiments show that a decrease in the carbon dioxide out- 

 put may take place as a direct effect of the ether on the protoplasmic 

 substance, when complications due to motion are excluded. This 

 effect may play a part in the phenomena observed in the previous ex- 

 periments (on tad poles, aquatic insects, and frog eggs) where the 

 cessation of motion is involved. 



