PHYSIOLOGICAL INTEGRATION IN ANIMALS. 377 



through these ramifying channels, injury of a single one 

 will cause a loss of blood that quickly prostrates the entire 

 organism. Hence the rise of a completely-differentiated vas- 

 cular system, is the rise of a system which integrates all 

 members of the body, by making each dependent on the in- 

 tegrity of the vascular system, and therefore on the integrity 

 of each member through which it ramifies. In 



another mode, too, the establishment of a distributing appa- 

 ratus produces a physiological union that is great in propor- 

 tion as this distributing apparatus is efficient. As fast as it 

 assumes a function unlike the rest, each part of an animal 

 modifies the blood in a way more or less unlike the rest, both 

 by the materials it abstracts and by the products it adds; 

 and hence the more differentiated the vascular system be- 

 comes, the more does it integrate all parts by making each 

 of them feel the qualitative modification of the blood which 

 every other has produced. This is simply and conspicuously 

 exemplified by the lungs. In the absence of a vascular 

 system, or in the absence of one that is well marked off 

 from the imbedding tissues, the nutritive plasma or the crude 

 blood, gets what small aeration it can, only by coming near 

 the creature's outer surface, or those inner surfaces which are 

 bathed by water. But where there have been formed definite 

 channels branching throughout the body, and particularly 

 where there exist specialized organs for pumping the blood 

 through these channels, it manifestly becomes possible for 

 the aeration to be carried on in one part peculiarly modified 

 to further it, while all other parts have the aerated blood 

 brought to them. And how greatly the differentiation of the 

 vascular system thus becomes a means of integrating the 

 various organs, is shown by the fatal result that follows when 

 the current of aerated blood is interrupted. 



Here, indeed, it becomes obvious both that certain physio- 

 logical differentiations make possible certain physiological 

 integrations ; and that, conversely, these integrations make 

 possible other differentiations. Besides the waste products 



