130 SYMBIOSIS 



tests, " physiologically younger " than those from which they 

 came. " The degree of rejuvenescence," so we learn, "is in 

 general proportionate to the degree of re-organisation in the 

 process of reconstitution of the piece into a whole." 



There is good reason to believe, even apart from this evidence, 

 that the virtue of the processes of re-organisation and reconsti- 

 tution here concerned lies in the fact of a simultaneous reduction 

 of what is best described as a " nutritive overflow." For under 

 what circumstances do such modes of propagation as usual with 

 these Planarians occur in Nature ? They occur chiefly among 

 parasites whose existence depends upon over-abundance of nutri- 

 tion and on sluggishness of life. A fair amount of biological 

 observation goes to show that in nearly all such cases good 

 results ensue from a reduction of conditions favourable to surfeit. 

 A return to moderation, be it voluntary or involuntary, may 

 have the effect, for instance, of bringing back the higher forms 

 of propagation conjugation or sexual reproduction proper 

 in the place of asexual reproduction. It may have the effect, 

 in other instances, of bringing back the male after many 

 generations of Parthenogenesis. Moderation, in short, is seen 

 to make for virility and health throughout the animal and 

 vegetable kingdoms. 



Evidence of similar good effects of abstemiousness in the 

 case of man was produced a few years ago by another investi- 

 gator, Professor Carlson, also of the Chicago University. He 

 tried on himself the effects of a protracted fast, and felt at the 

 end of it as if he had had a month's vacation in the mountains. 

 The mind was unusually clear, and a greater amount of mental 

 and physical work was accomplished without fatigue. A five 

 day's starvation period increased the vigour of the gastric 

 hunger contraction to that of a young man of twenty to twenty- 

 five (the age of the experimenter being thirty-eight). This 

 increased vigour was retained for at least three weeks after the 

 hunger period. A distinct rejuvenescence was thus observed 

 to result from a fast. Nor were the experiments confined to a 

 single individual or left unconfirmed by ordinary scientific 

 tests. 



