76 INTRODUCTION 



tubes, such as those of the bronchi, in order that they might 

 always remain open, and not be liable to collapse; and that 

 they might continue entirely free from blood, lest the liquid 

 should interfere with the passage of the air, as it so obviously 

 does when the lungs labour from being either greatly oppressed 

 or loaded in a less degree with phlegm, as they are when the 

 breathing is performed with a sibilous or rattling noise. 



Still less is that opinion to be tolerated which, as a two-fold 

 material, one aerial, one sanguineous, is required for the com- 

 position of vital spirits, supposes the blood to ooze through the 

 septum of the heart from the right to the left ventricle by certain 

 hidden porosities, and the air to be attracted from the lungs 

 through the great vessel, the pulmonary vein; and which, con- 

 sequently, will have it, that there are numerous porosities in 

 the septum of the heart adapted for the transmission of the 

 blood. But by Hercules ! no such pores can be demonstrated, nor 

 in fact do any such exist. For the septum of the heart is of a 

 denser and more compact structure than any portion of the 

 body, 'except the bones and sinews. But even supposing that 

 there were foramina or pores in this situation, how could one 

 of the ventricles extract anything from the other the left, 

 e.g., obtain blood from the right, when we see that both ven- 

 tricles contract and dilate simultaneously? Why should we not 

 rather believe that the right took spirits from the left, than that 

 the left obtained blood from the right ventricle through these 

 foramina? But it is certainly mysterious and incongruous that 

 blood should be supposed to be most commodiously drawn 

 through a set of obscure or invisible ducts, and air through per- 

 fectly open passages, at one and the same monrent. And why, 

 I ask, is recourse had to secret and invisible porosities, to 

 uncertain and obscure channels, to explain the passage of the 

 blood into the left ventricle, when there is so open a way through 

 the pulmonary veins? I own it has always appeared extraordi- 

 nary to me that they should have chosen to make, or rather 

 to imagine, a way through the thick, hard, dense, and most com- 

 pact septum of the heart, rather than take that by the open 

 pulmonary vein, or even through the lax, soft and spongy sub- 

 stance of the lungs at large. Besides, if the blood could per- 

 meate the substance of the septum, or could be imbibed from the 

 ventricles, what use were there for the coronary artery and vein, 





