234 Theories Treating of Inheritance 



out the organism are likewise undergoing continual 

 change, and because of these changes in relations new 

 conformations become produced at each stage of the 

 developmental process in a variety becoming ever more 

 complex." 178 



Nevertheless this does not hinder one, according to 

 that investigator, from considering the organism in its 

 entirety as a single physiological unit because of the idio- 

 plasmic identity of the nuclei of all its cells; a tiling 

 which he thinks, makes the inheritance of acquired 

 characters conceivable. 179 



For to explain the latter, Hertwig brings up the cases 

 of infection, immunization, and other similar examples, 

 in relation to which the organism can really be regarded 

 as a single entity. He quotes for instance the experi- 

 ments of Ehrlich who has succeeded by the administration 

 of extremely small doses of ricin in making rats immune 

 to this poison which is very powerful for them, and in 

 establishing the fact that this immunity was acquired not 

 only by the walls of the digestive canal with which the 

 poison comes into immediate contact, but also by all the 

 other tissues of the body, such as for example the sub- 

 cutaneous tissues and the ocular conjunctiva, and even 

 by the germ cells as was proved by the fact of the trans- 

 mission of this immunity to the young born of immunized 

 parents. 180 



Just as all the cells of the body are accessible to the 

 action of ricin and thanks to that fact all undergo a 

 material modification, which some of them, namely the 

 germ cells, transmit later to the descendants as an im- 



178 Oscar Hertwig, Die Zelle und die Gewebe. II. P. 75, 144, T 5^ 

 179 Oscar Hertwig: Ibid. II. P. 241. 

 180 Oscar Hertwijv: Ibid. II. P. 240!?. 

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