148 COPE. [Vot. III. 
i) THE LIMES 
The origin of the structures of the limbs of Mammalia will 
be considered under four heads. zrs¢. The proportions of the 
parts of the limbs. These, as is well known, vary exceedingly. 
The diversity is readily perceived on comparison of the four 
limbs of man, the horse, the whale, and the bat (Figs. 1-5—11- 
24); and nowhere is the relation of structure to a function of 
motion more obvious. 
Second. The number of the digits. The Condylarthra have 
five digits on both feet, and they are plantigrade. This character 
is retained in their descendants of the lines of Anthropoidea, 
Quadrumana, and Hyracoidea, also in the Bunotheria, Edentata, 
and most of the Rodentia. In the Amblypoda and Proboscidia 
the palm and heel are a little raised. In the Carnivora and Di- 
plarthra the heel is raised, often very high, above the ground, 
and the number of toes is diminished, as is well known, to two 
in the Artiodactyla and one in the Perissodactyla. 
Third. The fixed articulations. In the Condylarthra the 
bones of the two series in the carpus and tarsus are opposite 
each other, so as to form continuous and separate longitudinal 
series of bones. This continues to be the case in the Hyra- 
coidea and many of the Quadrumana, but in the anthropoid apes 
and man, the first row is partly displaced outwards so as to alter- 
nate with the second row, thus interrupting the series in the lon- 
gitudinal direction, and forming a stronger structure than that 
of the Condylarthra. In the Bunotherian, rodent, and edentate 
series, the tarsus continues to be without alternation, as in the 
Condylarthra, and it is generally identical in the Carnivora. In 
the hoofed series proper, it undergoes change. In the Proboscidia 
the carpus continues linear, while the tarsus alternates. In the 
Amblypoda the tarsus alternates in another fashion, and the car- 
pal bones are on the inner side linear, and on the outer side 
alternating. The complete interlocking by universal alteration 
of the two carpal series is only found in the Diplarthra. In the 
highest forms of the Rodentia and Diplarthra, the fibula and 
ulna become more or less coossified with the tibia and radius, 
and their middle portions become attenuated or disappear. 
Fourth. The ginglymoid articulations. These include the 
