28 THE PKINCIPLES OF HEREDITY 



46. Syphilis and tuberculosis have been instanced. But 

 syphilis and tuberculosis are never inborn. Presumably 

 they both depend on the presence of particular species of 

 pathogenetic organisms. The child acquires the disease as 

 much as the parent. No acquirement is transmuted into a 

 variation. It would be as reasonable to speak of ophthalmia 

 neonatarum, or of a bullet which had passed through a 

 mother and lodged in her foetus, as instances of the trans- 

 mission of acquirements. 



47. Haamophilia has been instanced. But haemophilia is 

 never acquired. It appears in the first instance as a varia- 

 tion, and for that reason is transmissible. Here the new is 

 confused with the acquired. 



48. Speaking practically, the few surviving scientific 

 upholders of the Lamarckian doctrine now limit themselves 

 to the contention that the effects of use and disuse are trans- 

 missible. This was the great thesis of Lamarck himself. 

 They admit, since acquirements are, at most, only "faintly 

 and fitfully " inherited, that mutilations and the like, which, 

 as a rule, are acquired by only a few individuals in a genera- 

 tion, and which do not greatly affect the rest of the body, 

 can have little or no influence on the race. But they 

 contend that the effects of use and disuse, which are acquired 

 by every individual during thousands of years and which 

 may profoundly affect the whole body, tend ultimately to 

 become " organized " into inborn characters ; the word " organ- 

 ized " being a vague word used to indicate a particular and 

 inexplicable change in the germ-plasm. Thus hares are 

 supposed to have become swift because their ancestors prac- 

 tised swift running. The giraffe is supposed to have a long 

 neck because its ancestors stretched upwards for food. The 

 elephant is supposed to have a short neck and a long 

 proboscis because its ancestors stretched their upper lips 

 rather than their necks. Similarly the snake is supposed to 

 have lost his limbs through the transmitted effects of disuse. 



