THE THEORY OF ANESTHESIA. 355 



in nerve-fibers treated with pure solutions of sodium and potas- 

 sium salts support this conception. 1 Changes in the electrical 

 condition of the cell are thus indices of changes in the colloids 

 forming the plasma-membrane, and especially in the lipoids. 

 Now, since the stimulation-process is always accompanied by 

 electrical variations, it seems probable that this process is itself 

 dependent on changes in the colloids of the plasma-membrane, 

 involving changes of permeability; correspondingly, artificial 

 alterations in the condition of these colloids should modify the 

 irritability of the cell. 2 In an important paper published in 1907, 

 entitled "Contributions to the Physical Chemistry of Stimulation 

 and Narcosis," 3 Hober applies this general conception to the 

 problem of narcosis essentially as follows: Stimulation is asso- 

 ciated with an alteration in the condition of the colloids of the 

 plasma-membrane, involving a general increase of permeability; 

 narcotics are those agents which prevent this alteration in the 

 condition of the protoplasmic colloids and hence prevent stimula- 

 tion. The colloids chiefly concerned are the lipoids; narcosis 

 depends on the collection of lipoid-soluble substances in the 

 lecithin of the plasma-membrane to a certain critical concentra- 

 tion, and on a prevention, by means of these substances, of 

 the colloid-process normally concerned in stimulation. Hober 

 showed that various anaesthetics (ethyl and phenyl urethane, 

 chloral hydrate, chloroform, hypnon) do in fact check the action 

 of rubidium and potassium salts in causing negative variation in 

 frogs' muscle. They also prevent the effect of potassium sulphate 

 in causing structural changes ("Auflockerung") in nerve. The 

 anaesthetic thus antagonizes the salt-action, just as it is known 

 to antagonize the stimulating action. Similar effects may be 

 produced by alkali earth salts, especially of calcium. According 

 therefore to Hober's hypothesis, the physico-chemical basis of 

 these antagonisms, and hence of anaesthetic action in general, 

 is an alteration of the colloids, especially the lipoids, of the 



1 Hober, Zentralblalt f. PhysioL, 1905, Vol. 19, p. 390. 



2 For a fuller account of Hober's views see his general article on "the physico- 

 chemical processes in stimulation" in Zeitschr.f. allg. PhysioL, 1910, Vol. 10, p. 173. 

 Also his textbook, " Physikalische Chemie der Zelle und der Gewebe," 4th edition, 

 1914. 



3 PJliiger's Archiv, Vol. 120, p. 492. 



