RATIONAL LIFE 299 



genera a gradual loss of the limbs a local or limited 

 degeneration. We have the common lizard (Lacerta) 

 with five toes on each of its well-grown fore and hind 

 limbs ; then we have side by side with this a lizard-like 

 creature, Seps, in which both pairs of limbs have 

 become ridiculously small, and are evidently ceasing 

 to be useful in the way in which those of Lacerta are 

 useful; and lastly, we have Bipes, in which the 

 anterior pair of limbs has altogether vanished, and 

 only a pair of stumps, representing the hinder limbs, 

 remain. No naturalist doubts that Seps and Bipes 

 represent two stages of degeneration, or atrophy of 

 the limbs. 1 This is a very partial or local atrophy, 

 which may help to illustrate degeneration as that may 

 apply to the whole organism. Degeneration may be 

 defined as a gradual change of the structure in which 

 the organism becomes adapted to less varied and less 

 complex conditions of life/ 2 Any new set of condi 

 tions occurring to an animal which render its food 

 and safety very easily attained, seem to lead as a rule 

 to degeneration : just as an active healthy man some 

 times degenerates when he becomes suddenly pos 

 sessed of a fortune, or as Rome degenerated when 

 possessed of the riches of the ancient world. 3 



That both men and animals are liable to degenerate 

 is certain; that man is the better for being con 

 strained to work in order to obtain food, just as an 

 animal is, must be no less clear; but we have to 

 inquire whether there is here such analogy as to 

 bring the cases of degeneration under common laws. 

 For this purpose, we shall proceed to that part of 

 the discussion directly concerned with human life. 



1 Advancement of Science, p. 26. 2 Ib. p. 26. 3 Ib. p. 27. 



