January 17, 1913] 



SCIENCE 



111 



him to remedy defects both of form and of 

 substance. g_ q_ Crittenden 



Bureau or Standards, 

 Washington, D. C. 



SPECIAL ABTICLES 



THE EFFECT OF ANESTHETICS UPON PERMEA- 

 BILITY 



There is much uncertainty as to the mode 

 of action of anesthetics and particularly as to 

 their effect upon permeability. While some 

 writers hold that anesthetics increase perme- 

 ability, others take the opposite view.' To 

 clear up this confusion appears to be a neces- 

 sary step toward a theory of anesthesia. 



A definite solution of this problem seems to 

 have been attained in the cases here described. 

 This result is due to the employment of quan- 

 titative methods without which it would not 

 have been possible. 



The experiments were made by measuring 

 the conductance of living tissues of a marine 

 plant, Laminaria. Under the conditions of 

 the experiment an increase or decrease of con- 

 ductance signifies a corresponding increase or 

 decrease of permeability.^ 



The anesthetics were mixed with sea water 

 and sufficient concentrated sea water was then 

 added to make the conductivity equal to that 

 of sea water. The material was then placed 

 in the mixture and its conductance was meas- 

 ured at frequent intervals. 



Material having resistance of 1.000 ohms' 

 was placed in a mixture of 990 c.c. sea water 

 plus 10 c.c. ether, to which was added suflicient 

 concentrated sea water to make its conduc- 

 tivity equal to that of ordinary sea water. In 

 the course of 10 minutes the resistance rose to 

 1,100 ohms: in the next 10 minutes it fell to 

 1,070 ohms; in 20 minutes more to 1,020 ohms, 



^ Cf . H'ober, ' ' Physikalisohe Chemie der Zelle 

 und der Gewebe," Dritte Auflage, 1911, pp. 219, 

 223, 489; R. Lillie, Am. Jour. Physiol, 29: 372, 

 1912; 30: 1, 1912; Lepeschkin, Ber. d. tot. Ges., 

 29: 349, 1911. 



' The method has been described in Science, 

 N. S., 35: 112, 1912. 



' All the figures in this paper refer to readings 

 at 18° G. 



and in 20 minutes more to 1,000 ohms. In the 

 next 20 minutes it dropped to 990 ohms, at 

 which point it remained stationary for a long 

 time. Subsequently it decreased very slowly, 

 but at exactly the same rate as the control 

 which remained in sea water during the ex- 

 periment. After 24 hours it had the same re- 

 sistance as the control. 



In order to find out approximately what 

 part of the resistance is due to the living pro- 

 toplasm the tissue was killed at the end of the 

 experiment by adding a little formalin: after 

 rinsing well in sea water the resistance was 

 320 ohms. This represents the resistance of 

 the apparatus and dead tissue; on subtract- 

 ing it from the resistance previously given we 

 obtain approximately the resistance due to the 

 living protoplasm. This may be called the 

 net resistance while the resistance before sub- 

 traction may be called the gross resistance. 

 In this experiment, therefore, the net resist- 

 ance before treatment with ether was 1,000 — 

 320 = 680 ohms and the net conductance 

 1 _^- 680 = .0014Y mho. The loss in net con- 

 ductance due to ether is 13 per cent., which 

 means a decrease of permeability amounting 

 to 13 per cent. 



It is evident that this decrease of permea- 

 bility is completely reversible and involves no 

 injury. The fact that after the resistance has 

 fallen to a stationary point it is 10 ohms be- 

 low the starting point does not indicate injury, 

 but only an increase in the conductivity of 

 the solution due to the evaporation of the 

 ether. 



In another series of experiments the effects 

 of the evaporation of the anesthetic were 

 avoided by constantly renewing the solution 

 by means of a steady current. It was then 

 found that the resistance, after rising rapidly 

 to 'a maximum, remained stationary for a 

 long time (often for two hours or more) at 

 the maximum point, afterward falling slowly 

 to the normal. This more prolonged exposure 

 to the anesthetic seemed to produce no in- 

 jurious effects. 



In these experiments the amount of ether 



' in the solution was 1 per cent, by volume. 



Smaller amounts of ether produced less effect: 



