606 On the Laws of Digital Reduction. [ October, 
leaving the great pair of claws in front for the purpose of tearing 
up the bark and getting into crevices in searching for insects. 
The Dendrolagus or tree kangaroo is another instance, but here 
the descent from the terrestrial kangaroos is too obvious to re- 
quire discussion. In studying the fossil kangaroos Professor 
Owen noticed that the fur-claws were not as rudimentary as in 
the living species, showing that at one time there was a more uni- 
form distribution of strains than now. 
Among fossorial animals it is usual to find the claws and toes 
well developed upon the fore limbs; this is so in the moles, ar- 
madillos, recent and fossil, and in the Geomyide, or gophers, where 
the distribution of strains is very unequal in respect to the fore and 
hind pairs of limbs. So, too, in the group iv which man has been 
included, where the strains are greatest upon the hind pair, as in 
animals that run rapidly or are capable of making great leaps, 
like dogs, cats, rabbits, tapirs, cavies, or guinea pigs. 
It seems to us the most convincing proof of the doctrine of de- 
scent to find man an instance of the same kind of specialization 
determined by the manner of the distribution of strains as is 80 
often found among the lower groups, such as the horses, sloths, 
jumping mice, and even-toed ungulates. We would not put him 
in respect to foot-structure among the true plantigrades, for un- 
like them the elements of the digits are not uniformly of the 
same strength and calibre. He might be somewhat clumsily 
called an inequidigitate plantigrade. “ i 
Now as to the osteological side of the question : in man the 
bones through which the line of greatest mechanical strain passes 
are the first digit, ento-cuneiform, navicular, calcaneum, and as 
tragalus. In the horse this line passes through the third digit, 
external cuneiform, navicular, astragalus, and calcaneum m the 
hind foot; through the third digit, magnum, scaphoid, and lunar 
in the fore foot. In the kangaroo through the fifth, but mainly 
through the fourth digit, the cuboid, calcaneum, and astragalus 
in the hind foot. It will be noticed also that in the highest mem- 
ber of the highest group it is the first digit that is specialized 5 
in the intermediate groups that the intermediate digits pape io 
cialized ; that next to the very lowest group it is the fourth digit , 
and, further, that there are corresponding chains of specializ 
bones which receive and distribute the strains.’ 
; ve 
1 It may be as well to note that birds belong in the category of types wik 
undergone digital reduction. The ostrich for obvious reasons 18 the ex 
é the 
Among reptiles, turtles and dinosaurs may be included, both of which stand near 
birds in the system. 
