INFLUENCE OF THE VESSELS UPON NUTRITION 157 



to attract a larger quantity of material from the blood 

 with greater readiness than it otherwise would have 

 done, or than it would be able to do, if the vessels were 

 in a state of contraction or less filled with blood. If, 

 therefore, it were to be objected to my view that in such 

 conditions the most favorable effects are often produced 

 by local abstractions of blood, this would be no proof of 

 its incorrectness. If we cut off or diminish the supply 

 of nutritive matter, we must, of course, prevent the part 

 from absorbing more than its wont, but, vice versd, we 

 cannot by offering it a larger quantity of nutritive mate- 

 rial straightway compel it to take up more than it did ; 

 these are two entirely independent cases. However apt 

 one may be to conclude (and however much I may be 

 disposed to allow, that at the first glance there is some- 

 thing very plausible in such a conclusion) that, from the 

 favourable effect which the cutting off of the supply of 

 blood has in putting a stop to a process which arose from 

 an increase of it, the process depended upon this increased 

 supply, yet I am of opinion that the practical fact can- 

 not be interpreted in this way. It is not so much an 

 increase of quantity, either in the blood as a whole or in 

 that portion of it contained in an individual part, which 

 is required in order that a like increase should forthwith 

 take place in the nutrition of that part, or of the whole 

 body, as that, in my opinion, particular conditions should 

 obtain in the tissues (irritation) altering the nature ot 

 their attraction for the constituents of the blood, or that 

 particular matters should be present in the blood (specific 

 substances), upon which definite parts of the tissues are 

 able to exercise a particular attraction. 



If you apply this doctrine to the humoro-pathological 

 conception of the processes, you will be able to deduce 

 from it that I am far from contesting the correctness of 

 the humoral explanations in general, and that I rather 



