NACHMANSOHN: CHEMICAL iM EC HAN ISM IN NERVES 401 



ularly significant, in view of the cliemical composition of these organs: 

 They contain 92 per cent of water and only 2 per cent of protein. 



In the weak electric organ of the common Ray, the concentration is 

 relatively low. If, in the three species mentioned, voltage and number 

 of plates per centimeter are compared with the concentration of cholin- 

 esterase, a close relationship becomes obvious. ^^' ^® 



A more detailed analysis has been carried out on the electric organ 

 of Electrophorus electriciis. This species is particularly favorable for 

 such studies, since the number of plates per centimeter, and conse- 

 quently, the voltage per centimeter, decrease from the head to the 

 caudal end of the organ (plates 2 and 3). The cholinesterase activity 



200 



400 



acH E 



Figure 2. Correlation between voltage and cholinesterase activity. 

 The voltage per cm. is plotted against the enzyme concentration. The dotted line is calculated 

 from the data obtained with the method of least squares; the fully drawn line calculated on the 

 assumption that the line goes through the point. 



decreases in the same proportion. If the electric changes are recorded 

 and compared with the enzyme activity of the same section, a close 

 parallelism is obtained between voltage and enzyme concentration 

 (figure 1). This is found not only in regard to the variations which 

 occur in the same specimen, but even for the variations between the 

 individuals, which are quite considerable.^^ 



A great number of experiments have been carried out on fish of 

 various sizes, covering a range of the action potential from 0.5 to 

 22.0 volts per centimeter. The quotient CH.E./V was found to be 

 20.7, with a standard deviation of only ±0.7 or 3.7 per cent. The 

 standard deviation for a single measurement is d=5.1 or about 25 per 

 cent. This is good uniformity for a quotient correlating physical and 



