Von Osten—though now embittered and pathetically silent—quietly continued his experiments up to his death, which took place in 1909. At first he had gone about his work alone, but he was joined subsequently by Karl Krall, who then became known in connexion with this work for the first time.
Many were the attempts made in certain quarters of the Press to account for the facts of the case; the very simple means of procedure employed by von Osten were scouted and the whole thing proclaimed to be based upon trickery, influence, secret signs, an abnormal degree of training, and what not—anything and everything was seized upon in order to come into line with ordinary opinion.
Then, in the year 1905, Karl Krall, of Elberfeld, began his experiments with Hans II, encouraging, as a foundation for the furtherance of his theories, the abilities already developed in this horse, while devoting a more profound measure of insight to the entire problem.
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.
It would take us too long should we attempt to enter into any detailed discussion on this point. Krall's book, "Denkende Tiere" ("Thinking Animals")[1], may be recommended as the best source for investigation for those desiring to know more on this subject.
It must in any case be admitted that the investigations 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."