C. M. CHILD AND L. H. HYMAN. 



these agents then we have a combination of excitation and de- 

 pression and in consequence of the differences in susceptibility, 

 the degree of excitation and the length of the excitation period 

 differ in different regions of the animals. Again, the degree of 

 excitation and the length of the excitation period vary with con- 

 centration of the agent. In the higher concentrations of anes- 

 thetics, ethyl ether for example, and to a lesser degree ethyl 

 alcohol, momentary excitation may be followed almost immedi- 

 ately by anesthesia and paralysis of the muscular system. 



The dyes used, Janus green, methylene blue and neutral red, 

 are all distinctly excitatory in action, Janus green being an in- 

 tense irritant, even in very low concentrations, e. g., 0.002 per 

 cent., while methylene blue and neutral red are less irritating in 

 their action. In general the higher the concentration of the dyes 

 in solution, the more intense the irritant action, but in low con- 

 centrations the excitation increases to some extent with the ac- 

 cumulation of the dye in the tissues. 



With this wide range of physiological and experimental con- 

 ditions available, it becomes possible to control and modify sus- 

 ceptibility relations to a considerable extent and so to determine 

 more definitely than would otherwise be possible various factors 

 concerned. 



In the following sections the susceptibility relations observed 

 under these various conditions are described and analyzed. The 

 figures although diagrammatic are all drawn from animals ac- 

 tually observed and indicate the degree of contraction of the body- 

 regions in each particular case. In each figure the intact por- 

 tions are indicated by continuous outlines, the disintegrated por- 

 tions by dotted shading, and arrows beside the figure indicate 

 the direction in which disintegration is progressing. Since the 

 course of disintegration in the tentacles is almost invariably basi- 

 petal and, with only occasional exceptions, very similar in all 

 tentacles of an individual, the figures show the tentacles only so 

 far as is necessary to indicate their condition in each case. Parts 

 of body or stalk already disintegrated are usually drawn only so 

 far as is necessary to indicate the course of disintegration in fig- 

 ures of later stages. 



While the stages and progress of disintegration indicated in 



