594 THE POPULAR SCIENCE MONTHLY 



the higher classes are not exempt from this iron law. Various causes 

 are mentioned for this fact. Marriages are contracted much later in 

 life among the wealthy, and, as a rule, they have fewer children; the 

 intellectual life seems to be unfavorable to the fecundity of women. 

 Eace suicide is more common among the higher classes. 19 It is hardly 

 necessary to mention that families of an extremely healthy stock, and 

 living under the most favorable conditions, are able to continue their 

 existence a much longer time. The remarkable vitality of the British 

 aristocracy is due to their athletic habits and to the fact that they spend 

 the greater part of the year on their estates in the country. Ammon 

 holds that the aristocratic classes of the continent " have favorable pros- 

 pects to perpetuate their family names only if they live on their estates 

 and devote themselves to agriculture and the chase." 20 



The Jews seem to form an exception to what has just been said. 

 They have been city dwellers from the time they left Palestine and 

 began to overrun the countries of the earth. There can be no doubt 

 that they are a very healthy race. In the struggle for existence, during 

 the endless persecutions they had to undergo in every country and at 

 all ages, only the strongest individuals survived. A process of natural 

 selection thus produced a vigorous race. The frugal and sober habits 

 and the faithful application of the sanitary precepts of the Mosaic code 

 also contributed greatly to produce a healthy people. But these influ- 

 ences are much less at work in modern times. The vitality of the Jew 

 will be greatly affected by modern city life as we find it in the city of 

 New York, where the great bulk of the Jewish population in this 

 country lives. Tuberculosis, the scourge of the white race, used to be 

 rare among the Jews, but the unsanitary life in the " sweat-shops " of 

 New York is also increasing its victims among this people. 21 



The rate at which city populations die out is much more rapid than 

 one would ordinarily suppose. Becent researches have thrown much 

 light on this process of elimination. Ammon, in his researches on the 

 population of Carlsruhe and Freiburg (two comparatively small cities) 

 established the fact that the city-born population decreases in the course 

 of two generations from 100 per cent, to 29 and 15 per cent. He sup- 

 poses that on an average the families who move from the country to a 

 city die out in the course of two generations. 22 Hansen found that one 

 half of the population of the German cities consists at all times of 

 immigrants from the country districts, and he concludes from this fact 

 that the city population renews itself completely in the course of two 

 generations. 23 We may safely apply these results, which have been 



"Ammon, " Natiirl. Ausl.," p. 297. 



"Ibid., p. 302. 



21 Jerusalem, Med. Blatter, Wien, 1909, XXXII., 181. 



22 Ammon, "Natiirl. Ausl.," p. 300. 



23 Hansen, "Drei Bevolkerungsstufen," 1889, p. 27. 



