448 PHYSICAL DETERIORATION & MICROBIC DISEASE 



children have been reared under identical conditions. This inquiry 

 might be made, though with difficulty ; for in the slums are any 

 number of people immediately derived from robust English and 

 Irish peasant stocks, and these, if biometricians are right, should 

 be physically superior to the rest of native slum population. 



733. Medical men trace physical deterioration to the direct 

 effect on the germ-plasm of such agencies as insufficient food, bad 

 hygiene, disease, and alcoholism. They have discovered that 

 apparently no British families of a purely urban descent of four 

 generations are in existence, and believe, therefore, that the germ- 

 plasm is poisoned so rapidly under urban conditions that the town 

 renews itself from the country in every two or three generations. 

 But the very magnitude of the migration into the town, combined 

 with constant intermarriages between the urban and rural popula- 

 tions, renders practically impossible a purely urban descent of four 

 generations. The absurdity of attributing the rarity of families of 

 pure and ancient urban descent to germinal deterioration is seen 

 very clearly when we consider the case of the Jews. These people, 

 who intermarry amongst themselves, are often desperately poor, 

 and are not specially clean and sanitary in their habits and 

 dwellings. Indeed numbers of them inhabit the worst slums. 

 Derived by an almost pure descent from the inhabitants of those 

 terrible slums, the ghettos of the middle ages, and rarely inhabiting 

 rural parts, they are the most extremely urban type in the country, 

 and are, nevertheless, under town conditions, the most hardy and 

 prolific type of all. Medical writers attribute the relative immunity 

 of the Jews to the superior care bestowed by Jewish women on 

 offspring. But while Jewish mothers in slums are, on the average, 

 noticeably more healthy 1 and temperate, 2 and, therefore, better 

 able to rear and suckle children than English women in the same 

 surroundings, neither they nor their children are appreciably 

 cleaner, nor are their dwellings better than those of the natives. 

 The fact appears to be, then, that Jews are especially healthy and 

 temperate in towns, merely because they are derived from a race 

 which has been fitted by prolonged selection to urban conditions. 

 At any rate, if all the facts, including the recent evolution of 

 civilized races, are taken into account, I can think of no other 

 explanation ; and none other has been suggested except that the 

 Deity takes particular care of His chosen people, or that the 

 religious training of the Jews results in better maternal acquire- 

 ments than Christian training, and so forth. The Chinese appear 

 1 See 435- * See 501. 



