724 
PHYSIOLOGY: A. G. MAYER 
in contact with an electrolyte solution; and if this be true, the rate of 
nerve conduction should be a function of the electrical conductivity 
of the medium, and also of the surrounding fluid. 
To further test this hypothesis, I determined the electrical conduc- 
tivity of Tortugas sea water when heated or cooled, and compared it 
with the rate of nerve conduction at corresponding temperatures. 
This shows that the rate of nerve conduction has a temperature co- 
efficient about two and one-half times as high as that of the electrical 
conductivity of sea water; as will appear in Table 11. 
TABLE II 
Illustrated by Figure 2 
TEMPERATURE C° OF THE 
SEA WATER 
RATE OF NERVE CONDUCTION IN 
CASSIOPEA. MEAN OF HARVEY, MAYER, 
AND GARY'S OBSERVATIONS 
RELATIVE ELECTRICAL CONDUCTIVITY 
OF TORTUGAS SEA WATER DETER- 
MINED BY KOHLRAUSCH'S METHOD 
23 
71.3 
88.9 
24 
76.3 
90.7 
25 
81.17 
92.6 
26 
85.8 
94.4 
27 
90.74 
96.2 
28 
95.47 
98.0 
29 
100.00 
100.0 
30 
104.47 
101.6 
31 
109.2 
103.5 
32 
113.4 
105.3 
33 
117.8 
107.1 
It will be recalled that Harvey (1911, Puhl. Carnegie Inst. Washing- 
ton, No. 132) was the first to show that the rate of nerve conduction in 
Cassiopea augments in nearly a straight line as the sea water is heated 
until about 36° to 38°C. where it suddenly falls off, thus giving a curve 
resembling that of an enzyme reaction. This has been confirmed by 
the later work of Mayer, and Gary; and I find that when the rate has 
begun to fall off, the original rate is not recovered upon cooling. This 
may possibly mean that the hypothetical enzyme has been partially 
destroyed; for if this decline were due merely to asphyxiation the rate 
should recover to a greater degree when the medusa is replaced in sea 
water of normal temperature. Moreover, the high temperature co- 
efficient of the rate of nerve conduction suggests that we may be deal- 
ing with a chemical reaction in which a compound is formed composed 
of sodium, calcium, and some proteid element; the degree of ionization 
of which is considerably affected by temperature in the manner suggested 
by Hardy, 1900; Quincke, 1902; and Bayliss, 1915, Principles of General 
Physiology, p. 77. 
