40 J. WIl.LIAM BUCHANAN 



in its inhibitory effect on the nervous stimulation of the Y region 

 by section. Winterstein, ('14) has shown that nervous tissue 

 itself may be narcotized without reduction in rate of oxygen con- 

 sumption. A number of experiments on head frequency were 

 performed with solutions of methyl and iso-butyl alcohol. The 

 results are in agreement with those obtained with chloretone, 

 chloroform, ether, and chloral hydrate, but no measurements of 

 their effects on the oxygen consumption of the pieces were at- 

 tempted. Further w^ork of this nature with the alcohols is 

 contemplated. 



One is justified in stating positively that the results presented 

 are in perfect accord with, and afford strong support to Child's 

 conception of the factors concerned in head determination in 

 Planaria. When one considers that the data on the experimental 

 control of head frequency now include a wide range of conditions 

 and agents, age, nutritive condition, mechanical stimulation, 

 temperature, KNC, and a number of anesthetics of different 

 types, all of which are known to affect quantitatively the phys- 

 iological gradient of the intact animal or the stimulating effects 

 of cutting and isolation in the pieces and that in most cases the 

 effects of the conditions and agents on the gradient or the meta- 

 bolic conditions in the pieces after section have been established 

 by measurement, it becomes evident that the relation between 

 head-frequency changes and the effects of the agents or condi- 

 tions on the metabolic conditions in the pieces is something 

 more than an interesting parallelism. None of the evidence 

 has been refuted and the facts upon which this dynamic concep- 

 tion of head determination is based have become formidable in 

 number and import. Both the problem and its answer have 

 come out of the material, and the control of head frequency has 

 been accomplished by the use of agents or conditions whose quan- 

 titative effect on the metabolic conditions has been determined 

 by known chemical methods. 



This paper is not primarily concerned with the problem of 

 anesthesia, but with the effects of the anesthetics on head fre- 

 quency and on the stimulation following section. The experi- 

 ments on oxygen consumption were not planned to investigate 



