1877.] On the Laws of Digital Reduction. 605 
ble inequality existed. The equality in existing species is no 
doubt due to the equality of tractile strains upon each one of the 
digits, owing to the peculiar method of climbing and hanging to 
the limbs of trees by the great hook-like claws. 
The frequent reduction in the number of toes in the foot be- 
fore it commences in the hand is seen in the carnivorous groups 
Felide (cats) and Canide (dogs), in odd-toed ungulates, in the 
swift-foot terrestrial Rodentia, and universally amongst such an- 
imals as perform locomotion entirely by leaping with the hind 
feet, as the kangaroos and jumping mice. Upon this point it 
may be observed that these creatures all more or less decidedly 
leap, or else pitéh the body through space in running, mainly by 
means of the hind limbs. The effect of this unequal distribution 
of strains has shown itself in the hypertrophy of certain digits 
and their consequent specialization at the expense of the atrophy 
of the others. The direction in which growth force is manifested 
is here determined, as it is determined in all kinds of work or ex- 
ercise, by the increased development of parts most exercised, 
and shows that the claims of a certain surgeon, who is said to 
have been able to tell the occupations of tradesmen by inspecting 
the development of the muscles upon the body are not without 
foundation. Two cases of this kind have fallen under my own 
observation, one in the person of a carpenter and another in that 
of a blacksmith. 
It may be well to note in this place that man, the only primate 
Whose feet serve exclusively for purposes of locomotion, belongs 
to the foregoing class. ‘The outer toes in man are weaker, shorter, 
and less developed than in any of the higher apes, and what may 
eventually be the fate of these outer toes, if, as many do, he 
eeps on wearing shoes that a savage would not wear for a single 
hour, combined with the structure now admirably conditioning a 
gradual reduction, only our descendants will be able to deter- 
mine a thousand years hence. 
The lines of bones through which strains have been directed 
are in some way determined by the uses which the feet serve in 
the life of the animal and its ancestral series. This is supported 
by the fact that where the strains to be overcome are equally dis- 
tributed amongst all the digits there is rarely any specializa- 
tion of toes. In aquatic, marine, and arboreal animals the distri- 
bution of strains is comparatively equal, and I now call to mind 
but a very few exceptions to this rule, which is but slightly af- 
fected by even these. -One case is the Cyclothurus, where, how- 
ever, the hind foot and tail are modified into grasping organs, 
