Toxic Effects dm- to High Temperature. 177 



If the rate of consumption of oxygen be taken as a measure of the 

 metabolism of the corals, it appears that the metabolic activity bears 

 an inverse ratio to the coral's ability to withstand the effects of carbonic 

 acid and their ability to resist high temperature follows nearly the 

 same law. It seems possible, therefore, that under the influence of 

 high temperature carbonic acid may accumulate in the tissues faster 

 than it can be eliminated, and acids being toxic would soon cause 

 death. 



In the case of the scyphomedusa Cassiopea, I find that for temper- 

 atures below 37 there is no time factor that is to say, if the pulsating 

 subumbrella ring deprived of sense-organs and having an entrapped 

 neurogenic contraction wave be taken from sea-water of about 29 

 and placed in water of 36 C., it at once assumes a rate characteristic 

 of this higher temperature, and this rate is the same as if the tempera- 

 ture had been slowly raised so that two or more hours elapsed before 

 the temperature rose from 29 to 36 C. Moreover, the reaction is 

 completely reversible, the rate returning at once to the original when 

 the ring is replaced in sea-water at 29. At about 37 or 38, however, 

 the rate of the nerve impulse begins to decline sharply, and I find that 

 this is subject to a time factor, the decline becoming more and more 

 pronounced as the heat, even though constant in temperature, is 

 continued. Moreover, when the superheated ring is replaced in sea- 

 water at 29 C., the pulsation is slower than it was before being sub- 

 jected to the excessive heat. A time factor for the effect of extreme 

 heat has been known since the time of Sachs (1865) and has been 

 studied by Blackmail (1905) and others. After about an hour, more or 

 less complete recovery of rate may take place, especially if the heat 

 had not been too great or exposure to its influences too long. In 

 other words, at injuriously high temperatures CO 2 may accumulate 

 more rapidly than the tissues can eliminate it and the time-factor, 

 according to my hypothesis, is due to this fact. 



Thus in a typical case, a nerve-wave in Cassiopea having a rate of 

 100 at 29.3 had the following rates when heated to 37.8 C.: 100 at 

 29.3, 125 at 35.6, 126 at 36.7, 127 at 37.3, 120 at 37.8. Thus the 

 nerve-conduction became more and more rapid up to 37.3 C., above 

 which it declined sharply, becoming 120 after being for about 20 

 minutes at 37.8 C. The animal was then taken from 37.8 C. and 

 replaced in sea- water at 29.3 C., and its rate declined at once to 80, 

 thus being 20 per cent less rapid than it was at the beginning of the 

 experiment; but after remaining in sea-water at 29.3 C. for nearly 2 

 hours the original rate was completely restored. 



It will be recalled that Blackman (1905) and Harvey (1911) ad- 

 vanced the theory that some enzyme might be destroyed by the exces- 

 sive heat, and, being essential to nerve-conduction, its loss caused the 

 rate to decline. It is also possible, however, that some toxic-acid 



