10 J. WILLIAM BUCHANAN 



head frequency occurs, but the number of normals is decreased. 

 The hitter eifect is obviously the result of the direct effect of the 

 KNC on the X cells of these pieces. The tendency to increased 

 head frequency in such posterior pieces is therefore somewhat 

 interfered with by the direct effect of the KNC on Rate X. 



If such alterations of head frequency are due to the prevention 

 of the stimulation of section and a differential depressing effect 

 of KNC on Rate X and Rate Y, the results ought to be similar 

 for all depressants under comparable experimental conditions. 

 In the present paper I purpose to present the results on head 

 frequency and on oxygen consumption of subjecting pieces from 

 the anterior zooid of Planaria dorotocephala to various concen- 

 trations of a number of narcotics. The work was begun in the 

 autumn of 1915. I desire here to acknowledge my deep obliga- 

 tions to Prof. C. M. Child, under vvhose direction the work was 

 done, for his stimulating interest and helpful suggestions and 

 criticism. I am also indebted to Dr. L. H. Hyman for valuable 

 suggestions and advice. 



MATERIAL AND METHODS 



A single species, Planaria dorotocephala, was used in this 

 study. Since it has been shown that the physiological condi- 

 tion of the animals controls the head frequency of the pieces to a 

 considerable extent, consistent and uniform results can be ex- 

 pected from standardized material only. The environment of 

 the animals in nature varies with respect to light, temperature, 

 food supply, and other conditions. For this work, therefore, 

 the worms after collection were kept in the laboratory for some 

 time before being used for experiment — at least two weeks and 

 in most cases several months — in order to bring the animals as 

 nearly as possible to the same physiological condition. Each 

 collection was kept in separate pans under approximately the 

 same conditions of light and temperature. The city tap-water, 

 because of its free chlorine content, was unfit for use, and the 

 water used in the pans was drawn from a well. The stocks 

 were fed on beef liver three times a week. In stocks so controlled, 

 size is the best index of physiological condition, and for experi- 



