1000 LIFE : OUTLINES OF GENERAL BIOLOGY 



Is Training Transmissible? — ^W^hen Prof. Pavlov, the distin- 

 guished Russian physiologist, was lecturing in Britain several 

 years ago he unfortunately put into circulation a curious tale in 

 regard to the hereditary transmission of the results of training. He 

 trained some white mice to associate the ringing of an electric bell 

 with the filling of their feeding-trough, so that after three hundred 

 lessons what is called a "conditioned reflex" was established, and 

 the mice came running whenever the bell was sounded, although 

 there was no food forthcoming as reward. This sort of learning is 

 well known among animals, both of high and low degree. But Pavlov 

 was understood to have said that the children of these mice required 

 only a hundred lessons, and the grandchildren only thirty. The 

 inference that the results of training were being transmitted was 

 corroborated in the next generation, when five lessons sufficed. This 

 story was so circumstantially reported that it found its way into 

 books, such as Prof. E. W. MacBride's Introduction to the Study of 

 Heredity ; and if it had been true it would have been one of the most 

 important experiments in the world. It would have served as a 

 welcome buttress of Lamarckism, and it would have put heart into 

 educational efforts. But the fact is that Pavlov has entirely with- 

 drawn his statements as to the hereditary transmission of the 

 "conditioned reflex", serious defects having been discovered in 

 the process by which the positive conclusions had been reached. 



Before Pavlov's revocation was published, somewhat similar test 

 experiments were made in 1924 by Dr. E. C. MacDowell, working 

 at the Carnegie Institution, Long Island. He trained white rats to 

 master a maze of the Hampton Court type, and afterwards did the 

 same with their offspring and grand-offspring. We do not gather from 

 his paper how many rats were used, but MacDowell's conclusion 

 stands out clearly that the training of the ancestors did not facilitate 

 the process of learning on the part of their descendants. "Children 

 from trained parents, or from trained parents and trained grand- 

 parents, take as long to learn the maze habit as the first generation 

 trained." 



A repetition of Pavlov's experiment was begun by Miss Isobel 

 Dean in 1925, working in the Zoological Laboratory in Aberdeen 

 University; but it had imfortunately to be discontinued after the 

 second generation. One striking fact was soon evident, that the 

 Aberdeen mice were much quicker in the uptake than those of 

 Petrograd. For the males there were hints of the establishment of 

 a conditioned reflex as early as the twenty-sixth meal; and by the 

 fortieth meal the association of food and bell had been acquired by 

 them all ! At that stage, whenever the bell began to ring, which was 

 two or three seconds before the door to the food was raised, there 

 was a general rush of the mice from the upper floor, where they all 

 were at the time. The response was so immediate, the mice eagerly 



