THE RACIAL EFFECTS OF DISEASE 259 



experience of diseases? If the Lamarckian doctrine be true, all 

 races exposed to such chronic maladies as tuberculosis should 

 steadily deteriorate ; for by such maladies the individual is never 

 strengthened in any known way, but, on the contrary, always 

 injured. His resisting power is lowered. Therefore, no matter 

 how slight and partial, how fitful and faint the inheritance of 

 parental injury, yet the effects accumulating during many genera- 

 tions should at last cause the race to trend towards extinction. 

 Is it, then, the fact that races afflicted by tuberculosis, or any 

 other agency which causes chronic ill-health, are steadily deterio- 

 rating, steadily becoming less and less capable of existence? On 

 the other hand, acute maladies confer a great measure of resisting 

 power on individuals who have experienced them and survived. 

 If this be inherited, no matter how faintly and fitfully, the race 

 should in time develop absolute inborn immunity, absolute in- 

 capacity to acquire disease. Is it, then, the fact, that races which 

 have long been afflicted by such acute maladies as measles, 

 chicken-pox, whooping-cough, and the like, have become quite 

 immune to infection ? Evidently the Lamarckian doctrine implies 

 racial effects due to disease which are very remarkable. Each 

 chronic disease must weaken the race till it perishes, each 

 acute disease must strengthen it till it is quite immune to that 

 disease. 



431. The hypothesis that variations are caused by the direct 

 action of the environment, though often confused with the 

 Lamarckian doctrine, is quite distinct from it. 1 It supposes, not 

 that the characters which arise in the parent through use or injury 

 are reproduced by the child under the influence of nutrition, but 

 merely that nutritive substances, waste products, toxins, and the 

 like, circulating in the blood, or otherwise acting on the germ- 

 cells, tend to alter the hereditary tendencies in the germ-plasm in 

 some definite way in such a way that the individual who 

 springs from the germ-cell is injured or benefited, weakened or 

 strengthened. At first sight this hypothesis is much more probable 

 than the Lamarckian theory. But it is only reasonable to suppose 

 that if the germ-plasm is altered at all by the direct action of the 

 environment, it is injured and devitalized, not benefited by ex- 

 posure to the toxins of acute diseases or by the general inter- 

 ference with nutrition which accompanies the chronic maladies. 

 At any rate, while it has often been held that parental ill-health 

 is a cause of filial degeneration, no one has suggested that syphilis, 



1 See 98. 



