212 COPE. (Vor. III. 
The typical gait of this class is the run or the jump. In the 
second class the limbs of one side strike the ground at the same 
time, and alternate with those of the opposite side. This class 
is represented by the pace. In the third kind of locomotion the 
opposite feet of different pairs strike the earth together, the line 
of identical movement being diagonal to the long axis of the 
body. The trot is typical of this kind of gait. The majority 
of gaits do not conform pre- 
cisely with these definitions, 
two feet rarely striking the 
ground at actually the same 
moment, but their mechani- 
cal action can be shown to 
be predominantly or entirely 
of the three kinds. The ef- 
fects of such action are as 
follows. In the simultaneous 
elevation and depression of 
the limbs of one pair, alter- 
nating with similar move- 
ments of the other pair, no 
torsion of the vertebral col- 
umn results. Inthealternate 
elevation and depression of 
the limbs of one side in co-op- 
eration, the vertebral axis is 
alternately depressed and 
raised again throughout its 
length on one side at one 
time. It is rapidly rocked 
from one side to the other 
during the pace and similar 
gaits, and here, also, there is no torsion. When the column 
is supported on opposite sides at its two extremities, as in 
the trot, it is rocked in opposite directions at the extremities. 
Thus, when one side is elevated anteriorly, it is depressed pos- 
teriorly, and wece versa. This motion produces torsion of the 
column, and especially of that portion which is free from fixed 
connections and braces, viz. : the lumbar region. Now an exam- 
ination of the gaits of animals shows that it is those which trot 
Figure 46. — Cervus canadensis trotting; 
from Muybridge, Animal Motion. 
