Vol. XXX. May, 1916. No. 5 



BIOLOGICAL BULLETIN 



THE THEORY OF ANESTHESIA. 



RALPH S. LILLIE, 



i 

 BIOLOGICAL DEPARTMENT, CLARK UNIVERSITY, WORCESTER, MASS. 



Anaesthesia, also termed narcosis, is a physiological condition 

 in which the normal responsiveness or automatic activity of the 

 living system organism, tissue, or cell is temporarily decreased 

 or abolished. The subjective accompaniment of this change in 

 higher animals is a more or less complete suppression of conscious- 

 ness, with consequent insensibility to pain; the term "anaesthe- 

 sia" refers more directly to this condition. By "narcosis" is 

 usually meant a temporary paralysis or anaesthesia produced by 

 chemical substances; this term has a more objective connotation; 

 and is the one usually employed in purely physiological discus- 

 sion. It is especially noteworthy that the condition may show 

 all gradations of degree, ranging from a comparatively slight 

 inhibition or insensibility to a state of profound depression in 

 which the organism is completely inert and shows no response to 

 even the strongest stimuli. Yet on the removal of the anaesthe- 

 tizing agent the normal properties and activities return. Reversi- 

 bility is thus an essential characteristic of the condition; this 

 peculiarity distinguishes it from the irreversible change of death. 

 There are, however, significant resemblances between these two 

 states, and in fact transitions from the one to the other are fre- 

 quent. Too prolonged or too profound anaesthesia may pass 

 into death; and most anaesthetic substances, if present in too 

 high concentration, soon cause irreversible and cytolytic changes 

 in cells. There is in fact evidence that in many instances 

 anaesthetic and toxic effects have the same essential physico- 

 chemical basis. The same cell-structures especially surface- 

 structures, e. g., plasma-membranes are primarily affected in 



