218 CARNEGIE INSTITUTION OF WASHINGTON. 



nearly doubled at 33°. The claw nerve of the male Limulus, however, does 

 not show so great a range as that of the female and thus the effects of tempera- 

 ture on the nerve fibers of different sexes are exactly similar to those on the 

 ganglia. 



The temperature coefficient of the nerve impulse is about 2 to 3 for each 

 10-degree interval, decreasing gradually as the temperature rises, but in no 

 case, if I am not mistaken, does the coefficient go above 2 at as high a tem- 

 perature as 27°. Even in Cassiopea, which lives at a temperature of about 

 30°, the temperature coefficient for nerve impulse is not quite 2 at tempera- 

 tures ranging from 27° to 33°. The wide difference between the coefficients 

 of the velocity of nerve impulse and the resting nerve metabolism seems to 

 indicate, at first sight, that nerve impulse is of a nature different from that of 

 resting metabolism in the nerve fiber. However, since the accumulation of 

 CO2 is known to be very detrimental to the conduction of the nerve impulse, 

 the gradual increase of the temperature coefficient of the velocity of the nerve 

 impulse as temperature rises may be due to the accumulation of the metabolic 

 by-products produced by steady increase of tissue metabolism as the tem- 

 perature is raised. This may explain why many curves of temperature 

 coefficient of the nerve impulse (Harvey) and regenerating activity (Goldfarb) 

 and many other physiological phenomena appear to be "enzymic curves" 

 rather than van't Hoff's curve of chemical reaction, and the possibility of 

 the operation of other simple physical factors, such as Snyder points out in 

 case of changes of viscosity in the physiological fluid, may be considered. 



However this may be, the fact seems to indicate that the fundamental 

 conditions for the conduction of nerve impulse are determined by metabolic 

 conditions in the nerve before stimulation. It is important, therefore, to 

 determine the temperature coefficient of the increase of CO2 production on 

 stimulation. 



III. Further Evidknce for the Increased CO2 Production in Nerve Fiber during 

 Stimulation, with Particular Reference to High Temperatures. 



It has been demonstrated that when a nerve impulse passes through the 

 nerve fiber, CO2 production is more than doul)led. Since the temperature 

 coefficient of the velocity of nerve impulse is not so great at higher temper- 

 tures as at lower, it is of interest to estimate the increased production of CO2 

 in the nerve fibers of tropical animals during stimulation. 



The determination made on the claw nerve of Limulus at Tortugas at 32" 

 to 33° shows that the production of CO2 on stimulation is about doubled, 

 which is less than that in other nerves determined at Woods Hole. Whether 

 this rather slight increase of CO2 on stimulation in tropical nerve is charac- 

 teristic of the nerves of all animals at high temperatures can not be determined 

 until similar investigations are made upon the nerves of other animals at 

 Tortugas as well as upon the nerves of the same species at Woods Hole. It 

 is quite possible that the comparatively low rate of nerve impulse in the claw 

 nerve of Limulus may be directly connected with less CO2 increase on stimu- 

 lation than is the case in other nerves which have a higher velocity of nerve 

 impulse. 



IV. Tissue Metabolism in Cassiopea xamachana. 



Since Cassiopea has been a subject of various important biological investi- 

 gations at Tortugas, it is of interest to test, with the biometer, the metabolic 

 activities of the animal under various conditions, in order to see how far the 

 metabolic factors are responsible for certain known physiological phenomena. 



