Introduction 1 1 



description, living in the depths of the sea, take in 

 and emit air by the diastole and systole of their arteries 

 through the infinite mass of waters ? For to say that 

 they absorb the air that is infixed in the water, and emit 

 their fumes into this medium, were to utter something 

 very like a mere figment. And if the arteries in their 

 systole expel fuliginous vapours from their cavities 

 through the pores of the flesh and skin, why not the 

 spirits, which are said to be contained in these vessels, 

 at the same time, since spirits are much more subtile 

 than fuliginous vapours or smoke ? And further, if the 

 arteries take in and cast out air in the systole and 

 diastole, like the lungs in the process of respiration, 

 wherefore do they not do the same thing when a wound 

 is made in one of them, as is done in the operation 

 of arteriotomy ? When the windpipe is divided, it is 

 sufficiently obvious that the air enters and returns 

 through the wound by two opposite movements ; but 

 when an artery is divided, it is equally manifest that 

 blood escapes in one continuous stream, and that no 

 air either enters or issues. If the pulsations of the 

 arteries fan and refrigerate the several parts of the body 

 as the lungs do the heart, how comes it, as is commonly 

 said, that the arteries carry the vital blood into the 

 different parts, abundantly charged with vital spirits, 

 which cherish the heat of these parts, sustain them 

 when asleep, and recruit them when exhausted ? and 

 how should it happen that, if you tie the arteries, 

 immediately the parts not only become torpid, and 

 frigid, and look pale, but at length cease even to be 

 nourished ? This, according to Galen, is because they 

 are deprived of the heat which flowed through all parts 

 from the heart, as its source ; whence it would appear 

 that the arteries rather carry warmth to the parts than 

 serve for any fanning or refrigeration. Besides, how 

 can the diastole [of the arteries] draw spirits from the 

 heart to warm the body and its parts, and, from without, 

 means of cooling or tempering them ? Still further, 



