240 THE THEORIES OF EVOLUTION 



gate themselves, in order to pass through narrow 

 spaces, their bodies have acquired a considerable length 

 not commensurate with their width. Under the cir- 

 cumstances, legs would serve no purpose and, conse- 

 quently, would not be used ; long legs would interfere 

 with the snakes' desire for gliding and short ones 

 could not move their body, for they can only have 

 four of them. Continued lack of use of the legs in 

 snakes caused them to disappear, although they were 

 really included in the plan of organisation of those 

 animals." 



This is observable, not only in the phylogenetic evo- 

 lution of the various animal orders, but in one given 

 individual in the course of its existence. "It is well 

 known that heavy drinkers, in an habitual condition of 

 inebriety, partake of very little solid food, and 

 hardly eat anything, for the liquids they absorb abun- 

 dantly and frequently suffice to nourish them. As 

 liquid foods, however, do not remain long in the 

 stomach or the intestine, the stomach and the intestinal 

 track of drunkards and of sedentary persons, who 

 apply themselves continually to intellectual work and 

 are accustomed to partake of very small quantities of 

 food, lose the habit of being distended. The stomach 

 gradually contracts itself and the intestine shrinks." 5 



On the contrary "the frequent use of an organ, 

 made constant by habit, increases the faculties of that 



6 Vol. I, pp. 240-247. 



