INTRODUCTION 69 



at all times either air or spirits, or fuliginous vapours, what 

 should then be said to Galen, who wrote a book on purpose to 

 show that by nature the arteries contained blood, and nothing 

 but blood, and consequently neither spirits nor air, as may 

 readily be gathered from the experiments and reasonings con- 

 tained in the same book? Now, if the arteries are filled in 

 the diastole with air then taken into them (a larger quantity 

 of air penetrating when the pulse is large and full), it must come 

 to pass that if you plunge into a bath of water or of oil 

 when the pulse is strong and full, it ought forthwith to 

 become either smaller or much slower, since the circumambient 

 bath will render it either difficult or impossible for the air to 

 penetrate. In like manner, as all the arteries, those that are 

 deep-seated as well as those that are superficial, are dilated at 

 tht same instant and with the same rapidity, how is it possible 

 that air should penetrate to the deeper parts as freely and 

 quickly through the skin, flesh, and other structures, as through 

 the cuticle alone? And how should the arteries of the foetus 

 draw air into their cavities through the abdomen of the mother 

 and the body of the womb? And how should seals, whales, 

 dolphins, and other cetaceans, and fishes of every 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 water? For to say that they absorb the air that is present 

 in the water, and emit their fumes into this medium, were to 

 utter something like a figment. And if the arteries in their 

 systole texpel fuliginous vapours from their cavities through the 

 pores of the flesh and skin, why not the spirits, which are said 

 to be contained in those vessels, at the same time, since spirits 

 are much more subtile than fuliginous vapours or smoke? And 

 if the arteries take in and cast out air in the systole and diastole, 

 like the lungs in the process of respiration, why do they not do 

 the same thing whtn a wound is made in one of them, as 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 con- 

 tinuous 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 com* 



