6oi THE HISTORY OF BIOLOGY 



has come into question. Isolated cases have been known of old of alleged 

 purely human intelligence in domestic animals. Shakspere in one of his com- 

 edies alludes to a horse, on show at the time, that was able to count; in 

 our own day one or two similar cases have certainly given rise to much dis- 

 cussion. Even professional biologists have believed, after investigation, in 

 the famous horses of Elberfeld, which performed operations of counting in 

 higher mathematics and other equally remarkable feats. On the other hand, 

 the authenticity of these cases has been very keenly disputed — Alfred Leh- 

 mann describes them unreservedly as self-deception on the part of the spec- 

 tators or conscious duplicity on the part of the exhibitor. At best, however, 

 it could only be a matter of abnormal receptivity to training, which cannot 

 be considered in any respect to characterize normal intelligence in the ani- 

 mals and thus cannot offer any guidance for judging the development of 

 the intelligence in the animal kingdom, which, however, has been very 

 generally asserted by those who have felt convinced of the reality of the 

 feats exhibited. In cases like these keen criticism is more than ever essential; 

 unfortunately many even distinguished biologists have shown themselves, 

 owing to their preconceived ideas, far stronger in their beliefs than clear 

 in their judgments, and this has been not least apparent in that much dis- 

 puted chapter, the psychic life of the animals. 



