Karl Krall, who lavished an untold amount of time and money on the question, has also raised it to an immeasurably higher plane. He has, indeed, placed a remarkable collection of carefully selected material at the service of the scientific world. With an unusual amount of devotion, backed by patience and a genuine affection for his charges, Karl Krall has carried on a work of investigation to which he assigns no narrow limits; pursuing his labours with a cheerful energy, fully convinced of the sacredness of his task. Anyone who has come into contact with Krall must feel respect for this man, whatever doubts he may harbour as to the results obtained. In 1908 Krall started work with two Arab stallions, Zarif and Mohammed. Both these animals learnt to count by means of rapping out the numbers with their hoofs on a board. One rap with the left fore-hoof always counted as "ten," while each rap with the right fore-hoof counted as "one" only. The number twenty-five was, therefore, composed of two left raps and five right ones. Spelling was similarly indicated by a system of raps meant to express separate letters of the alphabet. A pause followed after each number and the answers, being displayed to sight in the form of rows of numbers, it sufficed to place the letter thus indicated beneath its respective number in order to work out the reply. In the course of time these animals learnt the most varied forms of arithmetic, even to the extent of extracting the most difficult roots. They had, indeed, learnt to give answers which were, for the part, quite independent--thus supplying the most unexpected insight into their actual thinking and feeling. They also learnt the divisions of time, while every kind of experiment was undertaken in order to test their reasoning capacity. All these attempts and the majority of results were of such a nature that it became quite impossible not to realize that further persistence along the same lines of inquiry was bound to lead to a confirmation of the assurances already given by Karl Krall with regard to his pupils' "scholarship." Many diverse opinions were heard, while the number of serious adherents to the cause as well as that of its opponents increased. Special instances to which objection had been taken on the score of supposed "influence," or of "signalling," were carefully investigated by Krall in order to clear up any implied doubts. For this purpose a blind horse, by name "Bertho," was taken in hand, proof being thus provided to confute the mythical "code of signals" supposed to exist between master and pupil. Other tests undertaken with Bertho were equally successful; Krall was, in fact, always eager and willing to submit every objection brought forward to investigation, evident though it was, that his own vast experience amply sufficed to tip the balance in his favour.