158 ON VARIABILITY AND ADAPTATION 



The toxines circulating in the blood of the individual under- 

 going immunization must also affect the germ cells. They 

 must acquire immunity, and the individuals developed from 

 them must, subject to the law of loss already noted, have the 

 same properties. Now, as a matter of fact, this transmission of 

 acquired immunity has been occasionally noted ; where, for 

 example, both parents (rabbits) have been rendered immune to 

 the Bacillus pyocyaneus, the offspring have been found more 

 refractory to pyocyaneus infection, but in general the observa- 

 tions have been negative. This, as I have hinted, is only to be 

 expected on account of the easy detachment of, if I may so 

 express it, newly-acquired side-chains. It is, however, legitimate 

 to suppose that successive immunization through several genera- 

 tions will cause the new side-chains to become more and more 

 fixed, and that racial immunity is brought about by these means, 

 a view more probable than the alternative of mere " survival of 

 the fittest." 1 



Conversely, in those cases where immunity is not developed 

 in the case of chronic conditions like tuberculosis, we can, along 

 these lines, comprehend how the toxines weaken the germ cells 

 along the same lines as they weaken the general tissues of the 

 body ; and as the resistance of the body in general to a special 

 microbe and its products becomes less and less, so also the 

 idioplasm of the germ cells becomes less and less resistant, and 

 so from parental disease the offspring gains a peculiar suscepti- 

 bility to one special disease. So that, in short, from disease 

 acquired by the parents, a particular diathesis is developed, 

 a special susceptibility to the particular form of disease. 



Here Weismann would make the somewhat subtle distinction 

 that we are not dealing with the direct transmission of acquired 

 parental defects — that the toxines produce these results not by 

 acting on the body cells, but by direct action on the germ cells 

 — that the inheritance is blastogenic, not somatogenic. 2 This 

 is a sorry and almost Jesuistic play upon words. Let us grant 

 that they are of blastogenic origin ; they are nevertheless of 

 individual acquirement. The individual consists of body plasm 



1 It goes without saying that where both father and mother are immunized 

 through successive generations and the foetus — and its germ cells — acted upon 

 by the maternal blood and milk, the development of acquired inherited immunity 

 should become yet more assured. 



a Weismann, loc. cit. p. 410. 



