TOXICOLOGY AND PHARMACOLOGY 387 



leaving permanent changes. We thus arrive at the chief point in 

 the problem. The MEYER-OVERTON theory explains the conditions 

 under which a substance may act as a narcotic, but it does not show 

 why it narcotizes; in other words, what the essence of narcosis is. 

 Recent investigations, especially those of R. HOBER, have shown 

 that narcosis is brought about by a change in the state of swelling of 

 the nerve colloids by which the changes which would otherwise be 

 induced by the cell electrolytes upon stimulation are arrested. Ex- 

 perimentally we consider an organ narcotized if its irritability is 

 temporarily arrested or definitely changed. If we pass the im- 

 pulse of an electric current through a muscle it contracts. If the 

 ends of a muscle are attached to a galvanometer and we stimulate 

 the muscle the needle of the galvanometer makes a short excursion; 

 this is called the current of action. This is associated in no way 

 with the muscular contraction, for we may produce an electric im- 

 pulse in the nerve the same way and nerves do not contract. The 

 excursion of the galvanometer needle is the only evidence that the 

 nerve is stimulated. All these phenomena are temporarily arrested 

 as soon as the organ is narcotized. 



If we now see that normal irritability is manifest as the result of 

 an electrolytic process in which transitory changes in turgescence 

 occur, and that the turgescence of nerves and muscle colloids are 

 changed by salts, by which the irritability is consequently influenced, 

 we shall not doubt that there is a connection between turgescence 

 and irritability. When we find that the influence of salts upon the 

 swelling capacity of cell colloids, especially the lipoids, is placed in 

 abeyance or suspended by narcotics, the mass of evidence is con- 

 clusive. 



The connection between irritability and colloid turgor was dis- 

 cussed in Chapters XVII and XXI; the following passages will 

 show that narcotics arrest changes in turgescence. R. HOBER * 4 has 

 shown that the axis cylinders of nerve fibers swelled up in some 

 portions under the influence of neutral salts and shrank in others, as 

 is beautifully shown by staining with methylene blue. The phe- 

 nomenon is reversible. Swelling under the influence of neutral salts 

 does not occur when ethyl urethan narcosis is produced simultane- 

 ously. Accordingly, in this case the narcosis may be demonstrated 

 in the stained sections (see p. 336). A. R. MOORE and H. E. ROAF* 

 found that lipoid suspensions are precipitated by small quantities of 

 chloroform, alcohol, ether, etc., instead of being dissolved by them. 

 R. GOLDSCHMIDT and E. PRIBRAM * found a similar action of chloral 

 h} r drate and urethan in lecithin suspensions. 



According to S. J. MELTZER magnesium salts produce narcosis if 



