NUTRITION IN SENESCENCE AND REJUVENESCENCE 159 



complete starvation in filtered water. The curve ab, drawn as an 

 unbroken line in Fig. 57, is the susceptibility curve of ten starved 

 animals which have undergone reduction to a length of seven to 

 eight millimeters. The second curve ab, drawn as a broken line, 

 shows the susceptibility of ten newly collected, young, growing 

 animals of the same size as the reduced worms. A part of the 

 original stock was fed, while the others were starved, and the curve 



Stages 



II 



III 



IV 



Hours i 234567 



FIG. 56. Susceptibility of Planaria dorotocephala to KCN o.ooi mol. in relation 

 to nutritive condition and age: ab, susceptibility of well-fed, growing animals 7-8 

 mm. in length; cd, susceptibility of animals reduced by starvation from 15-18 mm 

 to 7-8 mm.; ef t susceptibility of well-fed animals 15-18 mm. in length. 



cd shows the susceptibility of these animals. During the three 

 months of feeding these worms have of course grown somewhat 

 older, but in full-grown animals like these the change in three 

 months is slight. But the susceptibility of the starving animals 

 has increased until it is about the same as that of young, growing 

 animals of the same size. 



Determinations of susceptibility by the direct method with 

 cyanide, alcohol, and ether as reagent have been made on several 



