CARBON DIOXIDE AS A NARCOTIC AGENT. 



457 



TABLE IT. 

 PERCENTAGE OF EGGS CLEAVED DURING EXPOSURE TO CO . 



It is evident from Table II. that with less than 30 per cent, 

 saturation the repression of cleavage is not complete, but only 

 partial. At a value of 30 per cent., repression is almost complete, 

 since only 7 per cent, and 44 per cent, of the eggs were able to 

 cleave in three and one third and five hours respectively. It will 

 be shown later in the paper that the effects of 30 per cent, and 

 40 per cent. CO., are so similar to those produced by greater 

 amounts, that it is reasonable to suppose that at a saturation of 

 40 per cent, and over, representing a tension of 300 mm. Hg or 

 more, the suppression of cleavage is practically complete. There- 

 fore not only can very small amounts of CO 2 in the surrounding 

 medium cause an appreciable delay in cleavage, but also its maxi- 

 mum action in suppressing cleavage is approached at values far 

 below saturation. 



Notwithstanding the prompt and extensive check upon cleavage 

 which carbon dioxide produces, the reversibility of its effects upon 

 returning the eggs to sea water serves to indicate that the action 

 has been of a narcotic rather than of a purely toxic nature. After 

 exposures of twenty minutes to sea water practically saturated 

 with CO 2 there are usually no abnormalities in cleavage, and 

 larvae develop which show little or no difference from the normal 

 controls. Following longer exposures, abnormalities appear, al- 

 though they are relatively few in number with exposures of less 

 than an hour. In spite of the presence of many abnormally 



