94 ASSIMILATION OF BLOOD. 



perfect, in regard to all those immeasurable minute par- 

 ticulars by which the blood is adapted for the nutrition of 

 every tissue, and the maintenance of every peculiarity of 

 each. How precise the assimilation must be for such an 

 adaptation, may be conceived from some of the cases in 

 which the blood is altered by disease, and by assimilation 

 is maintained in its altered state. For example, by the 

 insertion of vaccine matter, the blood is for a short time 

 manifestly diseased ; however minute the portion of virus, 

 it affects and alters, in some way, the whole of the blood. 

 And the alteration thus produced, inconceivably slight as 

 it must be, is long maintained ; for even very long after a 

 successful vaccination, a second insertion of the virus may 

 have no effect, the blood being no longer amenable to its 

 influence, because the new blood, formed after the vaccina- 

 tion, is made like the blood as altered by the vaccine 

 virus ; in other words, the blood exactly assimilates to its 

 altered self the materials derived from the lymph and chyle. 

 In health we cannot see the precision of the adjustment 

 of the blood to the tissues ; but we may imagine it from 

 the small influences by which, as in vaccination, it is 

 disturbed ; and we may be sure that the new blood is as 

 perfectly assimilated to the healthy standard as in disease 

 it is assimilated to the most minutely altered standard.* 



How far the assimilation of the blood is affected by any 

 formative power which it may possess in common with the 

 solid tissues, we know not. That this possible formative 

 power is, however, if present, greatly ministered to and 

 assisted by the actions of other parts there can be no doubt ; 

 as ist } by the digestive and absorbent systems, and pro- 

 bably by the liver, and all of the so-called vascular glands ; 

 and, 2ndly, by the excretory organs, which separate from 

 the blood refuse materials, including in this term not only 



* Corresponding facts in relation to the maintenance of the tissues 

 by assimilation will be mentioned in the chapter on NUTRITION . 



