Effect of Different Temperatures on the Medusa Cassiopea. 35 



observations thus far indicate that 0,^ for the rate of increase of the heart 

 beat, both of vertebrates and invertebrates, is about 2 to 3 for normal 

 temperatures. We may conclude that in the medusa, as in the heart, 

 the origination of stimuli in the sense-organs is dependent on the pro- 

 gressing of some chemical reaction. 



Mayer ^ believes that the pulsation is due to a constant formation 

 of sodium oxalate in the sense-organs. This precipitates the CaCl2 and 

 CaSO^ diffusing it from the sea-water, thus forming a slight excess of 

 NaCl and Na.SO^, which act as stimulants. The rate of formation of 

 Na oxalate (probably from carbohydrates) conditions the rate of pulsa- 

 tion. This, then, appears to be, in part at least, the reaction whose 

 increase in velocity with rise of temperature quickens the pulsation rate 

 at the same time. 



NERVE CONDUCTION. 



With the exception of Maxwell's paper on the pedal nerves of 

 ArioHmax, previous work on the influence of temperature on nerve 

 conduction has been confined to vertebrates. 



Snyder - calculated from Helmholtz's ^ observation on the frog a 

 tempera ture-coeflficient (Q^^) of 3.16; from Nicolai's ^ observations on 

 the olfactory nerve of the pike a value for Q^^ = 2.6 ; and from von Miriam 

 on the frog's ischiadicus, 0^^ = 1.95. In his own experiments, reported 

 in the same paper, Snyder also determined Q^, for conduction rate in 

 the frog's sciatic to lie for the most part between 2 and 3. 



Lucas ^ finds in the leg nerves (sciatic + tibial + sural) of the frog 

 Qjo for 8° to 18° and 9° to 19° = 1.64 to 2.08 with an average of 1.79. 



Maxwell,^ in 1907, working on the pedal nerves of Ariolimax, in 

 which the conduction rate is slow, found Q^^ to equal on the average 1.78. 



In this connection it may be of interest to mention Wolley's ^ paper 

 on the rate of conduction of a contraction wave in the frog's sartorius. 

 The latent period is also recorded. His results are as follows: 



The rate of conduction in muscle appears to be influenced by tem- 

 perature to the same degree as nerve. 



In Cassiopea the rate of nerve conduction is very much more 

 uniform than that of pulsation. It is not affected by currents in the 

 sea-water or by sHghtly disturbing the piece of tissue. Transferring from 



1 Mayer, A. G., Carnegie Institution of Washington, Pttb. No. 102, p. 129. 



2 Snvder, C. D., Am. Journ. Physiol., 22, p. 179, 1908. 



3 Helmholtz, Miiller's Archiv, 1850, pp. 345. 358. , o -, a , r 

 * Nicolai. Arch. f. d. ges. Physiol., 85, p. 113, 1901, and Snyder, Arch. f. 



Anat. u. Physiol., Phys. Abt., p. 113, 1907. 



^ Lucas, K., Journ. Physiol., 37, p. 112, 1908. 



8 Maxwell, S. S., Journ. Biol. Chem., 3, p. 359, 1907- 



' WoUey, W. J., Journ. Physiol., 37, p. 112, 1908. 



