vn] of the Seventeenth Century. 179 



He recognised that particles of the air taken into the lungs 

 enter in and become mixed with the blood. But true to his 

 position as a physicist dealing only with problems capable of 

 being solved with mathematical certitude, and refusing to 

 attempt to solve problems in any other way, he rejects all 

 vague chemical suggestions as to particular chemical substances 

 being drawn from the air and mixed with the blood. " The 

 " particles of the air mixed with the blood do not increase its 

 * flexibility, nor do they produce an effervescence in the heart 

 " by reason of their elastic force or of their nitrous nature." He 

 invents a physical hypothesis of molecular movement. He sup- 

 poses that the entrance of air into the blood produces continual 

 delicate oscillations {continuce motionis tremulce), which like 

 the pendulum of a clock regulate all animal actions. 



This exposition by Borelli appeared in print when his book 

 was published in 1680-1 ; but, as we have already said, much 

 which is to be found in the book had been publicly taught by 

 him many years- before, while he was at Pisa. Since, as he 

 himself admits, he rarely quoted authorities, it is difficult in 

 many cases to decide whether the view which Borelli is ex- 

 pounding is really his own, reached by him at an early date or 

 has been taken from some other author who had put it forth 

 before Borelli's book was finished for the press. And, as we 

 have seen, he never really finished the book ; he continued 

 labouring to improve it until almost the day of his death. We 

 may however conclude from the quotations just given that he 

 was acquainted with the views put forward during his life-time 

 by the English School of which I am about to speak ; and we 

 may also conclude that he rejected those views. To these we 

 must now turn. 



Robert Boyle as all know busied himself with the new views 

 as to the weight and pressure of air introduced by the observa- 

 tions of Galileo, Torricelli, and Pascal, by which the old plenum 

 doctrine of Descartes was overthrown. With his new pneu- 

 matical engine, or air-pump (which von Guericke had just 

 before introduced) he made many researches on the spring or 

 elater of air. 



He shewed in 1660 that even in a partial vacuum 



12—2 



