336 THE PRINCIPLES OF HEREDITY 



better conditions. But if it be meant that the conditions of 

 slum life weaken the race as such so that successive genera- 

 tions of individuals are born more and more innately defective, 

 then the statement is just as certainly untrue. It is founded 

 on a confusion between inborn and acquired traits. There 

 is not an iota of evidence that country children removed 

 shortly after birth to the slums are, on the average, more 

 robust than the natives, nor that town-bred infants removed 

 to the country tend to be inferior to their rustic playmates. 



520. Owing to this confusion between inborn and acquired 

 traits a belief is prevalent that urban families cannot persist 

 beyond the fourth generation without an infusion of country 

 blood. This statement is on a level with that with which 

 children are sometimes amused when they have lost a tooth. 

 They are told that a gold tooth will replace the missing one 

 if they refrain from putting the tongue in the cavity. No 

 child ever does refrain. Similarly, since intercourse between 

 town and country is very free, and since emigration from 

 country to town is very large, hardly a town family exists 

 that has not intermarried with country families or their near 

 descendants. Even if it were true that urban families tend 

 to become extinct within four generations, it would prove, 

 not that the race deteriorates in towns, but only that selec- 

 tion is so stringent that the birth-rate tends to fall below the 

 death-rate. Country blood does not strengthen city blood. It 

 weakens it, for it has been less thoroughly purged of weak 

 elements. Slums are not a creation of yesterday. They 

 have existed in many countries from prehistoric times. 

 Races that have been much exposed to a slum life are not 

 inferior physically nor mentally to those which have been 

 less exposed. Thus, for example, the Chinese, who have 

 been subjected for a longer time and to a greater extent to 

 these influences than any other race, are certainly not inferior 

 to the Dyaks of Borneo. The Jews, also, are a case in point. 

 Europeans are not inferior on an average to the savages of 

 the Western Hemisphere. Were the latter placed under the 

 frightful conditions which prevail in our large towns, they 

 would not only deteriorate individually, but perish en masse. 

 The history of civilization is, in effect, the history of the 

 gradual evolution of the power to resist the lethal influ- 

 ences which surround the town-dweller. As we have seen 

 already, without this evolution civilization would have 

 been impossible. 



521. To sum up : slum life weakens individuals exposed 

 to it ; but this acquired weakness is not transmitted to 



