ENLARGEMENT OF PARTS FROM USE. 15 
exhibited to a class of students, this large second toe was 
mistaken for the hallux (fig. 8). This observation is of 
interest, the large size of the first toe and the great 
development of its muscles are owing to the greater use 
and importance of the hallux in mammals which main- 
tain an erect, or semi-erect, position when walking along 
the ground as in man, or climbing trees as in monkeys 
and phalangers. Humphry, in reference to the large 
development of this toe, says, “ Man literally stands in 
the animal world on his great toe.” 
Fic. 8.—Enlargement of the second toe subsequent to 
amputation of the hallux. 
The same remarks apply to the thumb: in man 
increased function develops its special muscles, thickens 
the bone, and toughens the nail. Even among quadru- 
mana the pollex may be absent (Ateles) ; in such a high 
form as the chimpanzee the thumb is slender, short, and 
insignificant. In man we may attribute the dispropor- 
tion of the hallux and pollex, in comparison with the 
neighbouring digits, to inheritance through a long line of 
ancestors of gradual increments of size induced by 
