172 C. M. CHILD 



nearly doubles. In the case of chloral hydrate a much greater 

 increase occurs. Certain other anesthetics, salicylainid, benza- 

 mid, monacetin, on the other hand, show a decrease in the coeffi- 

 cient of distribution with rise in temperature. Meyer finds 

 that the anesthetic action of all these substances varies at differ- 

 ent temperatures with the coefficients of distribution. Thus the 

 anesthetic effect of alcohol and chloral hydrate increases with 

 rising temperature, while that of salicylamid, benzamid, and 

 monacetin decreases. 



In Meyer's experiments tadpoles were used and the concen- 

 tration of the anesthetic which would just produce complete 

 anesthesia was determined. In other words, these results were 

 obtained with vertebrates in which the nervous system contains 

 large quantities of lipoid. Moreover, only the minimal concen- 

 tration capable of producing narcosis was determined. It is 

 very probable that in such an experiment with such material the 

 coefficient of distribution is an important, perhaps the most 

 important factor in determining the narcotic action, but it does 

 not necessarily follow that this is the case in all other organisms. 

 In Planaria, for example, there is no such accumulation of lipoids 

 in the central nervous system as in vertebrates, and the narcotics 

 which I have used have little if any greater effect on the nervous 

 system than on other cells of the body, so far as can be determined. 

 In fact it was shown in the preceding paper (Child '12 a) that 

 development of the nervous system might go on in a concentration 

 of narcotic which practically inhibited completely all other devel- 

 opmental processes. 



Moreover, planarians which have been fed to repletion or dur- 

 ing a considerable period on mammalian brain tissue do not show 

 any decrease in physiological resistance to the action of alcohol 

 in the concentrations used with the direct method: on the con- 

 trary, their resistance may be much greater than that of other 

 animals which have been less heavily fed or fed on other kinds of 

 food. The accumulation of lipoid substance in the bodies of the 

 animals apparently does not decrease their resistance below that 

 of animals fed on lean beef: the beef -fed animals usually show 

 the lower rate of resistance because their rate of reaction is higher. 



