198 Historical 



explanation of the effect of the vacuum. It appears, however, that 

 for the academicians of the Cimento, a vacuum acts simply by the 

 removal of air. Furthermore, their translator and commentator 

 van Musschenbroeck explains it very clearly when he says: 



If we wish to know exactly how long a little bird can do without 

 air, let him be plunged under water; for then he cannot breathe air, 

 and he is immediately in a situation similar to a vacuum. 



These notes of van Musschenbroeck 4 also contain a very curious 

 description of the phenomena presented by an animal subjected 

 to the action of a vacuum, with an interpretation of the causes of 

 death, an extremely interesting interpretation, although it savors 

 of the false ideas of the epoch about the pulmonary circulation: 



We shut a rabbit in a glass receiver, and by means of the pneu- 

 matic pump drew out all the air; the animal at first was uneasy, 

 sought air, swelled up all over; its eyes protruded, it defecated, 

 sought a way out all around the vessel, sat up hardly breathing, 

 grew weak and fell in convulsions, lay down on its side, and finally 

 died; all these things happened in half a minute, after the pump began 

 to work and rapidly removed all the air from the vessel: the whole 

 body of the animal lost its air and was deflated; then when we opened 

 the chest, we found the lungs small, collapsed, solid, heavier than 

 water. The whole body of the animal swells in the vacuum because 

 the ventricle and the intestines contain much air, which, when it is 

 no longer compressed by the outer weight of the atmosphere, expands 

 in all directions as a result of its elasticity and distends the abdomen. 

 But the blood and the other humors have elastic air mingled with 

 their parts, which then, not being compressed, expands, recovers its 

 elasticity and distends all the vessels, so that all the body of the 

 animal must swell in all parts, especially the eyes, the humors of 

 which contain much of this air; experimentation has taught me this, as 

 I have tried to prove in my dissertation De aeris existentia in omnibus 

 animalium humoribus. 



Moreover, the animal enclosed in a vacuum cannot inhale air into 

 its lungs, and although it tries to expand its chest, and often repeats 

 this expansion, nevertheless nothing enters from the outer part of the 

 lungs into the air vessels or vesicles. That is why the contractile force 

 natural to all fibres compresses the vesicles; the lungs collapse, become 

 denser, and specifically heavier than water; but whereas the vesicles 

 attached to the extremities of the tracheal artery are compressed, the 

 circulation of the blood is hampered in the arteries and the veins 

 which surround the whole vesicular surface in abundance, and in those 

 which are situated in the interstices left around each vesicle. But in 

 this adult animal, the blood of the whole body, pumped out by the 

 right ventricle of the heart, must pass through the vessels of the lungs 

 into the left auricle and ventricle, so that from there it can be 

 pumped out into the parts of the body. When the vesicles of the 

 lungs are contracted and compressed in the vacuum, the blood vessels 



