Robert Sommer. Animal Psychology. Published by Quelle and Meyer in Leipzig, 1925

S. begins his book on animal psychology with a chapter on the history of animal psychology. This is followed by the chapter "Animals and Man". In this chapter S. expresses the basic idea that the scientific study of animal psychology must be made on an anatomical basis, rooted in the morphological and embryological features of animals. The third chapter, "Straightened gait, arm and leg," leads to the conclusion that in each species of the animal kingdom studied psychologically special attention must be paid to the general structure of the body, chiefly to the structure of the limbs with respect to their adaptability to certain external circumstances.