196 The English School [lect. 



" What part however this aereal salt plays in animal life it 

 " is not easy to understand. It is at all events probable that 

 " the nitro-aereal spirit, mixed with salino-sulphureous particles 

 " of the blood, excites in it a needed fermentation. We must 

 " not however suppose that the effervescence of the blood takes 

 " place in the heart alone ; it takes place also in the pulmonary 

 " vessels before the blood reaches the heart, and afterwards in 

 " the arteries, no less than in the heart itself." 



The word ' effervescence ' shews that he had read Sylvius. 

 Possibly, or perhaps we may rather say probably his acute mind 

 had, pondering much over fermentations, begun to grasp some 

 new 7 ideas about these mysterious processes, and had he lived 

 we might have learnt from him things which did not come until 

 much later. 



Touching thus upon fermentation, he turns aside to note 

 that he is not forgetful of that ' fermentum ' of a mysterious 

 character supposed to exist in the left ventricle, the ferment of 

 van Helmont's fifth digestion; but he scornfully rejects the 

 idea. Then he passes on to have a tilt with Descartes, who, 

 great philosopher, but amateur physiologist, as he was, had not 

 as we have seen grasped the force of Harvey's arguments, and 

 contended against Harvey that the beat of the heart was an 

 expansion due to the rarefaction of the ventricular contents. 

 Mayow had no difficulty in following Harvey and Lower 

 in the proof that the blood was driven out of the heart by 

 the contraction of the muscular walls. The heart, he says, 

 is nothing but a muscle, very little different in its action 

 from other muscles. And he clenches his argument against 

 Descartes with two remarkable experiments. "If in the 

 "heart of an animal just dead, filled not with blood, but 

 " with water or some simple liquid, you excite a movement 

 " like that which takes place in systole, the contents of the 

 " ventricle are forthwith ejected, not indeed by reason of a 

 'fermentative explosion, for such 'in this case certainly cannot 

 " take place, but simply because the ventricles are contracted." 

 Besides it is very certain that the movement of the heart can 

 not be due to the rarefaction of the blood ; for sometimes the 

 heart, cut clean out of the body, may be seen to beat, although 

 all the blood has already been driven out of the ventricles. 



