204 Mayow 



And this will be made still clearer by what is to be 

 said below. Still I will not deny that the movement 

 of the lungs, and the compression of the blood-vessels 

 occasioned by the fall of the thorax in expiration, 

 contribute not a little to send the blood through the 

 lungs ; but it is by no means to be supposed that this 

 is the only use of respiration. 



Hence some think that respiration serves a further 

 purpose, that of churning, forsooth, and dividing into 

 the smallest particles the thicker venous blood. For 

 otherwise (as they say) the blood would be separated 

 into distinct parts, namely, serum and a purple sedi- 

 ment. But neither is this the chief use of respiration. 



For any air, however impure, would suffice for such 

 a movement of the lupgs and for the churning of the 

 blood ; but air vitiated by contagion, or air which has 

 often been sent out from the lungs, is by no means 

 suitable for respiration and the support of life. With 

 respect, then, to the use of respiration, it may be 

 affirmed that an aerial something essential to life, 

 whatever it may be, passes into the mass of the blood. 

 And thus air driven out of the lungs, these vital 

 particles having been drained from it, is no longer fit 

 for breathing again. But this will be made clearer by 

 the following experiment. 



For if, by means of bellows attached to the trachea 

 of an animal, a dog for example, the lungs are in- 

 flated, but in such a way that, through openings 

 made here and there at their extremities, some of the 

 air may pass out, the loss of which must be supplied 

 by the bellows that the lungs may not collapse ; in 

 this case, I say, the animal will live. And yet that 

 sort of agitation of the blood cannot take place in 

 lungs which are kept inflated to the utmost. More- 

 over, though the movement of the lungs entirely 



