282 SCIENCE PROGRESS 



and publishing are not covered, so that more subscribers are 

 urgently required if the work is to be continued and developed. 



Yours faithfully, 



W. R. B. Prideaux, B.A., 

 Librarian of the Reform Club, London; 

 General Editor of the " Index to Periodicals." 



THE INTELLIGENT RAT 



From Enoch Karrer 

 Department of Commerce, Bureau of Standards, Washington 



Dear Sir,— In the last issue of Science Progress there 

 appears an article on " The Mathematical Amoeba, " bearing 

 upon animal intelligence. Will the following observations be 

 of sufficient interest to you for publication ? 



Observation on the behaviour of the rat, indicating that 

 the rat may learn by experience. 



The incident here recorded occurred in the chemical room 

 of the Physical Laboratory of the United Gas Improvement 

 of Philadelphia, in the fall of 1915. The first record made of 

 it was on October 24, 191 5. 



There is reason to believe that only one rat, is concerned 

 here ; for, after one rat was trapped, there were no further 

 evidences of the presence of rats. 



This particular rat had been carrying away the half-bars of 

 " Ivory Soap " to the shelves in an adjoining instrument-room 

 and devouring them there, previous to the discovery that it was 

 carrying the soap into the compartments of a table built against 

 the north side of the same room, which contained the sink with 

 the soap against the west wall. The table was 82 cm. high, 

 100 cm. wide, and of the length of the room. 



In the closed compartment below the table were kept the 

 stock bottles of acids. The rat had entrance into these com- 

 partments from the rear of the end about 6 m. from the 

 sink. The sink was 83 cm. above the floor. 



The habit of the rat was to carry the bar of soap from the 

 sink to this acid compartment (7 m.), where it devoured the soap 

 and gnawed off the paper labels marking the acid containers. 



A test with litmus showed these labels to be slightly acid, 



