ERRORS ATTRIBUTED TO ARISTOTLE. 199 



windpipe are connected "it is hollow." If he had 

 meant to speak of one of the pulmonary veins, or of 

 any of the cavities of the heart, he would have used the 

 terms Tropot, or icoCkias which he always employs for these 

 parts. 



According to Aristotle, then, the air taken into the 

 lungs passes, from the final ramifications of the bronchial 

 tubes into the corresponding branches of the pulmonary 

 blood-vessels, not through openings, but by transudation, 

 or, as we should nowadays say, diffusion, through the 

 thin partitions formed by the applied coats of the two 

 sets of canals. But the " pneuma " which thus reached 

 the interior of the blood-vessels was not, in Aristotle's 

 opinion, exactly the same thing as the air. It was " atfp 

 TTO\VS pecw KOI aQpoo? " (Be Mundo," iv. 9) subtilised 

 and condensed air ; and it is hard to make out whether 

 Aristotle considered it to possess the physical properties 

 of an elastic fluid or those of a liquid. As he affirms 

 that all the cavities of the heart contain blood (F), it is 

 clear that he did not hold the erroneous view propounded 

 in the next generation by Erasistratus. On the other 

 hand, the fact that he supposes that the spermatic arte- 

 ries do not contain blood but only an alfjuarS)^ vypov 

 (" Hist. Animalium," iii. 1), shows that his notions re- 

 specting the contents of the arteries were vague. Nor 

 does he seem to have known that the pulse is character- 

 istic only of the arteries ; and as he thought that the 

 arteries end in solid fibrous bands, he naturally could 

 not have entertained the faintest conception of the true 



