364 PHYSIOl OGICAL DEVELOPMENT. 



tissue- forming matters taken from the alimentary canal into 

 the blood, is not largely draughted off elsewhere, this local 

 growth may go on. But if many other sets of muscles are 

 similarly active, the abstraction of tissue- forming matters at 

 various places, will so far diminish their abundance in the 

 blood, as to reduce the supply available at any one place for 

 growth : eventually leaving sufficient for repair only. 



Though we lack data for thus interpreting specificall}' 

 the repair and growth of other active tissues, yet we may see, 

 in a general way, that a parallel interpretation holds. For 

 if any tissue that consumes, transforms, excretes, or secretes 

 matters that pass into it from the blood, is not formed of the 

 same constituents as these matters it transforms or excretes ; 

 or if it does not undergo waste proportionate to the quantity 

 of matter it transforms or excretes ; then it seems fairly 

 inferable that along with any unusual quantity of such 

 matters to be transformed or excreted, the plasma passing into 

 it must bring a surplus of the materiale for its own repair 

 and growth. 



