ANALYSIS OF FORM REGULATION WITH THE 

 AID OF ANESTHETICS. 



C. M. CHILD. 



During the last year and a half the writer has carried on an 

 extensive series of experiments on the influence of certain anaes- 

 thetics on the course and results of form regulation in Planaria 

 dorotocephala Woodworth. Since the method has proved to be 

 of considerable value and since it will be some time before the 

 results of these and other experiments planned for the future can 

 be presented in full, it seems desirable to present briefly and 

 without extended comment the most important features of the 

 work up to date as an illustration of the value of the method and 

 the results to be attained by it. 



In my experiments thus far I have used chiefly alcohol, ether 

 and acetone-chloroform, known commercially as chloretone. 

 Although alcohol is much less strongly anaesthetic than many 

 other substances its action is in general similar in kind to that of 

 the substances commonly known as anaesthetics. The results 

 with the three substances mentioned are practically identical so 

 far as the more general features are concerned, though various 

 differences of detail appear, which need not be considered here. 

 Incidentally, however, it may be noted that these differences in 

 the effects of the different anaesthetics serve to some extent as a 

 means of determining the specific differences in the effects of dif- 

 ferent anaesthetics on the metabolic processes : how far they 

 will prove to be of value in this direction only the future can 

 determine. 



In my experiments various concentrations of the three sub- 

 stances have been employed, but the most characteristic results 

 in general have been obtained with alcohol 1.5 per cent., ether 

 0.4-0.5 per cent,, chloretone 0.025-0.0375 per cent. These 

 concentrations cause a considerable deathrate, but the results in 

 the pieces which do not die within the first week or ten days are 

 very uniform, so far as pieces of the same size and from the same 

 region of the body are concerned. Alcohol has been used to a 



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