estigations undertaken by
Krall have shed a flood of light on the problem of the capacity for
thought latent in our higher animals, enabling him, as we have seen, to
lay down--within certain limits--in how far and in what way the
existence of this capability can be _proved_ where the horse is
concerned. Up to the commencement of the Great War these investigations
were continued, a number of different horses being used for the
purpose.

In the year 1912 I became acquainted with a new contribution towards
the question of animal psychology in the person of a Mannheim dog
called "Rolf."

The manner in which Rolf's gifts revealed themselves was disclosed in
the columns of the "Muenchner Nachrichten" as follows:

"OUR DOG ROLF

"_By Frau Paula Moekel_ (nee _von Moers, in Mannheim_)

"Anyone possessing an intelligent dog of his own will probably
occupy himself far more with it than he is wont to do with other
animals. This has been the case with our Rolf, a two-year-old
Airedale terrier, which has already attained to celebrity. It was
accident that led to our discovery of his talent for doing sums
correctly. Our children were sitting together at work on their
home-lessons, and one of my little girls--seized with a fit of
inattention--was unable to solve her very easy task, viz., 122 plus
2. At length, and after the child had stumbled repeatedly over this
simple answer, my patience was at an end, and I punished her. Rolf,
whose attachment to the children is quite touching, looked very
sad, and he gazed at Frieda with his expressive eyes as though he
was anxious to help her. Seeing this I exclaimed: 'Just see what
eyes Rolf is making! It looks as if _he_ knew what you do not!' No
sooner had I said this than Rolf, who had been lying under my
writing-table, got up and came to my side. In surprise I asked him:
'Well, Rolf, do you know what two plus two amounts to?' Whereupon
the animal tapped my arm with his paw _four times_--we were all
speechless! After a little while we asked him again--'5 plus 5?'
Here, too, the correct answer was forthcoming, and thus on the
first day did we question him up to a hundred, and with equal
success. After that verbal instruction became my daily occupation
with the dog, in the same way that one might teach an intelligent
child, Rolf entering readily into everything, indeed, we seemed to