e alone, and needed to direct only it and
not the entire head toward the questioner, in order to focus
comfortably, one could not conclude as to his line of vision from the
direction of the head. Since, furthermore, in the horse the pupil is
hardly distinguishable from the darkly pigmented iris and since the
white sclerotic is hidden by the eyelids, except when the eye is turned
very much, it is difficult to determine what direction the eye is
taking. I once purposely stepped backward to the horse's flank, so that
he had to turn his eye far back and thus the outer border of the iris
and the white sclerotic coat became visible and all doubt concerning the
line of vision was removed. This doubt could never arise in the case of
the dog, the median plane of whose head is always directed toward the
object fixated, and Zborzill is justified in saying, as he does, in his
discussion of training of the kind mentioned on page 177, "But any
careful observer can immediately guess the manner in which such a dog
has been trained."[64] If Hans had chanced to possess so-called
"glass-eyes"--in which the dark pigment is wholly or partly lacking, so
that the black pupil is clearly defined against the lighter
background,--then no doubt could ever have arisen concerning the
direction of the eye, and Hans never would have come to be regarded as
the "clever" Hans.

[Footnote AC: I can find examples of supposed suggestion in the case
of animals given only by Rouhet.[61] He says that by means of
suggestion he taught a half-year old half-blooded mare-colt which he
had raised himself, to fetch and carry, and this in a very short
time. In order to indicate to the colt what was wanted, Rouhet would
concentrate with his whole mind upon the object intended (a watch),
and at the same time he would bend forward slightly. In the third
test, that is at the end of fifteen minutes, he had accomplished his
purpose, and in the tenth lesson, no more mistakes occurred. The
colt would fail to respond, however, as soon as he refrained from
making any gestures, or was in a laissez faire frame of mind, or
when he thought of other things. He therefore believes that there
must have been some kind of immediate, though inexplicable,
connection between the brain of the trainer and that of the horse. I
think the explanation is evident: the connection was not as he
thought, an immediate one, but arising thr