188 CARNEGIE INSTITUTION OF WASHINGTON. 



Winterstein's theory that death from heat is due to asphyxiation appears 

 to be refuted by these experiments. 



E. N. Harvey (1911) found that if the sea-water be heated the rate of nerve- 

 conduction in Cassiopea augments in a right-hne ratio up to a certain point 

 and then rapidly dechnes just before death ensues. 



In 1917 I found that this temperature curve, up to its maximum point, 

 has no time-factor. That is to say, the rate at 35° C. is the same whether the 

 medusa be placed at once in 35° C. or warmed slowly for several hours until 

 it arrives at this temperature. Moreover, the normal rate for 29° is regained 

 almost immediately when the medusa is replaced in this normal temperature. 

 But when the rate is declining, on account of injuriously high temperature, 

 I find that a time factor is involved, the decline becoming more pronounced 

 as the heat is continued. Also, if after this the medusa is replaced in sea- 

 water of 29° C., its former rate is much reduced and may never be recovered, 

 although if exposure to the heat was not too long or the heat not too excessive, 

 a slow recovery is usually observed, so that after a few hours the rate may 

 again become normal. 



It will be recalled that Harvey (1911) advanced the theory that some 

 enzyme might be destroyed by the excessive heat, and being essential to 

 nerve-conduction its loss caused the rate to decline. It seems now probable, 

 however, that in excessive heat carbon dioxide accumulates in the tissues 

 faster than it can be eliminated. It is easy to see how an acid of this sort 

 might be eliminated and the rate gi-adually restored when the animal is 

 replaced in cool sea-water, whereas if an enzyme were destroyed it might not 

 so readily be replaced. 



In any event, the theory of the toxic effect of uneliminated acid seems 

 more in accord with the facts than does Winterstein's asphyxiation theory or 

 the theory that death from heat is due to coagulation of proteid substances. 



Death occurs at too low a temperature for coagulation in most if not all 

 proteids; and, when killed, the animals are fully relaxed, as shown by Harvey. 

 Moreover, coagulated proteins could not readily be eliminated when the 

 animal was restored to water at normal temperature. 



Report on Experiments made at Tortugas in 1917, by J. F. McClendon. 



Metabolism of Cassiopea xamachana. 



It was found that the metabolism of Cassiopea, as indicated by the heat 

 produced, CO2 eliminated, and oxygen consumed, was increased when more 

 oxygen was added to the sea-water and decreased when part of the oxygen 

 was removed from the sea-water. No oxygen is consumed and no CO2 

 given off if no oxygen be present, yet the animal survives more than 7 hours 

 in this condition. This was also true when only the umbrella of the cassiopea 

 was used. It was found that the metabolism of the mesogloea is practically 

 zero, and therefore all the metabolism of the umbrella takes place within less 

 than a millimeter of the surface and the effect of diffusion of oxygen into the 

 cells on the metabolism is correspondingly small. The pulsations of the 

 umbrella circulate the sea-water, and hence every cell is as close to the circu- 

 lating medium as is the case with an animal with a circulatory system. The 

 effect of oxygen concentration on metabolism is not due to diffusion phenom- 

 ena especially limited to this type of animal, and we may assume that the 

 results are of general significance in physiology. The direct application of 

 these results to man would be the possible effect of the activity of the respira- 

 tory and vasomotor centers on the so-called basal metabohsm. 



