30 J. WILLIAM BUCHANAN 



region by exposure to stronp; solutions of alcohol can exert no 

 different iative influence on the X cells and vice versa. One is 

 justified in stating that head frequency can be controlled to a 

 limited extent by exposure of the pieces to certain solutions of 

 ethyl alcohol, but that the probable inhibition of stimulation 

 resulting from section is masked in the oxygen-consumption 

 measurements of pieces under such conditions by the amount 

 of oxygen utilized in oxidizing the alcohol. 



EFFECT OF WEAK SOLUTIONS ACTING FOR ENTIRE PERIOD OF 



REGENERATION 



In the group of experiments just described we have seen that 

 the head-frequency changes in pieces subjected to relatively 

 strong solutions of anesthetics for short periods after section 

 result from two sorts of effects of the agents on the differentia- 

 tive and developmental processes of the X cells: 1) the direct 

 effect on these processes tending to decrease head frequency 

 and, 2) what may be called an indirect effect tending to increase 

 head frequency through elimination by the anesthetics of the 

 stimulation of the Y region which ordinarily acts as an inhibitor 

 of head formation. If we employ concentrations so dilute as" 

 not to inhibit to any appreciable degree the stimulation of the 

 Y region by section, we may expect the direct effect of the agents 

 on the X cells to be the chief cause of any changes in head fre- 

 quency that may result. It was with this object in view, i.e., 

 a study of the direct effect of the anesthetics on the X cells in 

 pieces from different levels, that a series of experiments was 

 undertaken in which A, B, and C pieces were subjected during 

 the entire period of two weeks to concentrations of the anes- 

 thetics so dilute as not to inhibit the stimulation of the Y region 

 by section. 



\ In all the experiments of this nature so far performed meas- 

 urements of the oxygen consumed by the pieces in the weak solu- 

 tions of the anesthetics and that consumed by their controls in 

 water show that the stimulation of section takes place to the 

 same extent in these weak solutions as in water. The indirect 

 effect of the anesthetics tending to increase head frequency by 



