1002 LIFE : OUTLINES OF GENERAL BIOLOGY 



which should be critically examined by those sensitive to statistical 

 fallacies, was to show on the part of the trained tank-rats a pre- 

 dominance of the dim route more decided than the slight pre- 

 dominance in the same direction which marked the behaviour of 

 the control rats. To the cold-blooded outsider it does not seem that 

 the difference is very striking ; and it is not claimed that the experi- 

 ments have as yet shown that there is in the course of generations 

 any regular increase of facility in learning the lesson. But the results 

 certainly justify an open mind and the continuation of these and 

 similar experiments. 



Supposing there is evidence of the Lamarckian transmission of 

 the effects of training, MacDougall inquires into the nature of that 

 which is transmitted. "What is that function which seems to be 

 accentuated in successive generations of the tank-rats as a conse- 

 quence of the training process?" He is inclined to answer: "A general 

 increase of timidity or caution, a greater susceptibility to fear, an 

 increased strength or sensitivity of the fear instinct." Whether this 

 specifically prompts to avoidance of the illuminated pathway, the 

 expert declines to say at present. But the less specific the response, 

 the less is its convincingness as regards Lamarckism, for general 

 increase in timidity and "nerves" may surely arise as a germinal 

 variation, apart from the particular experiences in the individual 

 lifetimes. But our thanks are due to MacDougall for continuing these 

 laborious experiments for six years and for seventeen generations 

 — "representing in human terms a period of some five centuries". 

 To say the least, he has kept this momentous question open: Are 

 the results of individual experiences representatively transmissible ? 



Alcoholic Rats. — ^Numerous experiments have been made in 

 America to test the hereditary effects of subjecting successive 

 generations of rats to alcohol fumes. A recent investigation, by 

 Prof. F. B. Hanson and Florence Heys, of Washington University, 

 St. Louis, dealt with ten treated generations of albino rats {Mus 

 norvegicus alhinus) and corresponding controls. The precise problem 

 was this: Do the descendants of treated rats, having ten generations 

 of alcoholic ancestry, possess any greater power of resistance to 

 alcohol fumes than the descendants of control rats of entirely 

 non-alcoholic ancestry ? The outcome of the experiments was to show 

 that no increased resistance to alcohol acquired by individuals during 

 their lifetime is in any degree passed on to their progeny. There was 

 no cumulative effect of ten generations of acquired resistance, 

 and no inheritance ; the individuals of each generation re-acquired 

 the resistance as their parents and grandparents had done before 

 them. 



Increased resistance to alcohol fumes is a physiological character, 

 gradually built up within the system, involving complex chemical 



