June 27, 1913] 



SCIENCE 



961 



retards or arrests activity in many eases; 

 e. g., the nerve cells of vertebrates are very 

 susceptible to lack of oxygen ; nerve trunks, 

 on the other hand, are relatively insuscep- 

 tible. Cell-division — e. g., in developing 

 egg-cells — usually ceases if the oxygen sup- 

 ply is insufficient. Contractile activities 

 are decreased or abolished. Many organ- 

 isms, however, show only slight immediate 

 effects ; this is true of many Protozoa ; Vor- 

 ticellffi, for instance, remain contractile for 

 some time after simple removal of oxygen 

 from the medium, although they are at 

 once paralyzed by anesthetics. Such facts 

 oppose the view held by Verworn and 

 others, that the anesthetic acts primarily 

 on the oxidative mechanism of the cell. It 

 is true that the rate of oxidations in active 

 tissues is lowered during anesthesia, but 

 this effect is rather a consequence than a 

 cause of the lessened activity. Obviously 

 wherever free oxygen is necessary to the 

 normal activities of a tissue its withdrawal 

 will arrest those activities. But the effects 

 produced by lack of oxygen are not to be 

 identified with anesthesia because of such 

 incidental resemblances. 



There are also a number of physical con- 

 ditions that may deprive a cell temporarily 

 of irritability. Thus mechanical shock may 

 have this effect, which, however, is prob- 

 ably to be regarded as essentially a conse- 

 quence of over-stimulation, causing abnor- 

 mal prolongation of the refractory period.- 

 The same is probably true of the insensi- 

 bility produced by strong electrical cur- 

 rents. Under certain conditions, however, 

 the electric current may produce effects 

 closely resembling typical anesthesia. 

 This occurs when a weak constant current 

 is passed through an irritable tissue like 

 muscle or nerve ; during the flow of the 



- This apparently corresponds to the period of 

 increased permeability and depolarization accom- 

 panying stimulation. 



current the irritability of the tissue is modi- 

 fied in the neighborhood of the two elec- 

 trodes, being heightened at the cathode 

 and lowered at the anode ; and in this latter 

 region the nerve may become completely 

 insensitive to stimuli that ordinarily cause 

 strong excitation. The inexcitable state 

 thus produced is called "aneleetrotonus"; 

 it is in reality a form of local anesthesia, 

 and as such has been employed for the alle- 

 viation of pain in sciatica and similar con- 

 ditions. Muscle is affected in a similar 

 manner; the frog's heart may thus be rend- 

 ered locally incapable of contraction, as in 

 the simple class-experiment familiar to all 

 physiologists. This action of the current 

 probably depends on its altering the elec- 

 trical polarization normal to the membranes 

 of the irritable elements — only in a direc- 

 tion the inverse of that causing stimula- 

 tion.^ There is much evidence that the 

 state of polarization of the semipermeable 

 membranes bounding the irritable elements 

 is an important factor in determining the 

 degree of responsiveness to stimulation; 

 the facts of electrotonus indicate that by 

 altering the polarization by an external 

 current the irritability of the tissue may be 

 changed in the direction either of increase 

 or of decrease. 



Irritability may, however, be more read- 

 ily modified by the use of chemical sub- 

 stances than by any other means, and, as is 

 well known, many such substances are in 

 daily use in medical and surgical practise 

 for procuring local or general insensibility 

 to pain — hence the application of the 

 name "anesthetic" to the large class of 

 substances possessing this property. When 

 we inquire into the chemical nature of such 

 substances we find that anesthetic property 

 is confined to no special class, but is ex- 



^ /. e., reinforcing instead of diminishing the 

 normal or physiological polarization of the mem- 

 branes. 



