38 J. WILLIAM BUCHANAN 



In the light of this dynamic conception of head determination, 

 the data on the effects of chloretone on head frequency and on 

 oxygen consumption of the pieces when subjected to various 

 concentrations for short periods after section may be explained 

 in detail and serve as a basis for comparison with the effects of 

 the other anesthetics employed. The chloretone results permit 

 the following general statements: First, that, within certain 

 limits, short period exposures are as effective as long in increas- 

 ing the head frequency in C pieces. The causes of this increase 

 must therefore be exerted very soon after section. The events 

 which are known to occur in C pieces placed in water immediately 

 after section are the wound stimulation of the X region and a 

 relatively great stimulation of the Y region. But the rate of me- 

 tabolism of the X region is known to remain high, while the stimu- 

 lation of the Y region disappears after a number of hours. Con- 

 sequently, we must look to the effect of the chloretone solutions 

 on the Y region in these short-period exposures for the factors 

 causing the increase in head frequency. In the measurements 

 of oxygen consumption the data demonstrate that in the chlore- 

 tone solutions employed the stimulation of the Y region does not 

 occur. The relation between the increase in head frequency in 

 C pieces after exposure to the chloretone solutions and the pre- 

 vention of the stimulation of section during the period of exposure 

 is regarded as causal for the reasons already given (Introduction 

 and p. 37). There is no intent here to imply that the wound 

 stimulation of the X region is not also inhibited in C pieces by 

 the anesthetic. Child, in his paper on the effects of KNC on 

 head frequency (Child, '16), gives data showing that the general 

 head frequency of C pieces may be increased by subjection of 

 the pieces to certain solutions of KNC, but that the number of 

 normal heads in such series may be decreased. The conclusions 

 drawn from the data are that the effect of the prevention of 

 stimulation of the Y region by the KNC overbalances the effect 

 on the X region, but that the effect on Rate X shows up never- 

 theless in the less complete regeneration of the anterior ends of 

 the higher types. In the present w^ork the agents used were not 

 nearly so powerful protoplasmic poisons as KNC, and this effect 

 on Rate X in C pieces is indistinguishable except in a few cases. 



