I 4 6 EXPERIMENTAL EVOLUTION LECT. 



stand-point of physiological variability ; but there is 

 something more that Professor de Tarchanoff has seen 

 and proved. The brain of the new-born guinea-pig, 

 for instance, does not answer to electrical stimulation 

 during the first days doubtless because it is not yet 

 developed enough. If it could be artificially developed 

 or retarded in its growth and progress, it is likely that 

 the moment at which electrical excitability exists 

 could be hastened or retarded, and that, similarly, the 

 moment at which the eyes open could be at will 

 hastened or retarded. Methods are not wanting to 

 allow the performance of the experiment, and 

 Professor de Tarchanoff has artificially hastened the 

 development by means of some phosphorus mixed 

 with the food, and by means of cerebral hyperaemia in- 

 duced by occasionally hanging the animals head down- 

 wards, while the reverse position and a slight degree 

 of alcoholism have been enough to render cerebral 

 development much slower. The result was exactly 

 what might have been expected ; when the develop- 

 ment is retarded, excitability and sight are retarded, 

 and another fact is noticeable : locomotion is also more 

 difficult and is attained later, because the causes which 

 retard the cerebral development inhibit more or less 

 all functions which are dependent upon the brain. 

 Professor de Tarchanoff thinks that it might be 

 possible, by repeating the same experiments on the 



