178 THE INDUCTIONS OF BIOLOGY. 



and, if recovery ensue, the blood will seem to have returned 

 to its previous condition : yet it is not as it was before ; for 

 now the same poison may be added to it with impunity." 

 * * # " The change once effected, may be maintained 

 through life. And herein seems to be a proof of the assimil- 

 ative force in the blood ; for there seems no other mode of 

 explaining these cases than by admitting that the altered 

 particles have the power of assimilating to themselves all 

 those by which they are being replaced : in other words, all 

 the blood that is formed after such a disease deviates from 

 the natural composition, so far as to acquire the peculiarity 

 engendered by the disease : it is formed according to the 

 altered model." Now if the compound molecules of the 

 blood, or of an organism considered in the aggregate, have 

 the power of moulding into their own type, the matters 

 which they absorb as nutriment ; and if, as Mr Paget 

 points out, they have the power when their type has been 

 changed by disease, of moulding all materials afterwards 

 received into the modified type ; may we not reasonably 

 suspect that the more or less specialized molecules of each 

 organ, have, in like manner, the power of moulding the 

 materials which the blood brings to them, into similarly 

 specialized molecules ? The one conclusion seems to be a 

 corollary from the other. Such a power cannot be claimed 

 for the component units of the blood, without being con- 

 ceded to the component units of every tissue. Indeed the 

 assertion of this power is little more than an assertion of the 

 fact, that organs composed of specialized units are capable 

 of resuming their structural integrity, after they have been 

 wasted by function. For if they do this, they must do it by 

 forming from the materials brought to them, certain special- 

 ized units like in kind to those of which they are composed , 

 and to say that they do this, is to say that their component 

 units have the power of moulding fit materials into othei 

 units of the same order. 



The repair of a wasted tissue may therefore be considered 



