DYNAMICS OF MORPHOGENESIS 157 



concentration of the reagent, etc., and also with various internal 

 factors. In worms or pieces in similar physiological condition 

 and under given external conditions, the time when disintegra- 

 tion begins and its rapidity are uniform to a high degree. 



The close relation between death and disintegration is shown in 

 various ways. For example, in KCN 0.001 m. at a temperature of 

 20°C. distinct movements of a given part can often be induced 

 within fifteen minutes of the time when disintegration of that part 

 begins. When concentrations of the anesthetics are used which 

 are sufficiently high to kill the animals almost at once, disinte- 

 gration occurs within a few minutes after the animals are placed 

 in the reagent, sometimes beginning within five or ten minutes. 



In cases where different regions of the animal or piece die at 

 different times, we usually find certain parts of the piece still 

 showing active movement, while others are already disintegrating 

 or completely disintegrated. 



In general then death is quickly followed by disintegration. 

 This fact affords an easy means for determining approximately 

 the time of death of an animal, a region of the body or a piece in 

 a given concentration of alcohol, KCN, etc. 



3. The relation between le^igth of life in depressing agents and rate 



of reaction 



Early in the course of my experiments it was found that the 

 length of life in a given concentration of the agent used was dif- 

 ferent according to the physiological condition of the animals and 

 in pieces, according to the size of the piece and the region of the 

 body from which it was taken. Moreover, in different concen- 

 trations of a given reagent the relation between certain animals 

 or pieces was not the same. At first the results appeared hope- 

 lessly complex, but I was convinced that there must be some way 

 of discovering the factors upon which they depended and finally, 

 after some eight months of work it became evident, first that a 

 relation existed between the physiological resistance of the ani- 

 mals or pieces and their rates of reaction, and second, that the 

 character of this relation was dependent upon the concentration 

 of the reagent used. These relations between length of life or 



