Theories and Experiments 199 



are also compressed, nothing passes from the right ventricle of the 

 heart 'into the left, the blood is not pumped to the brain, the cere- 

 bellum, or the other parts of the body, and the circulation of the 

 blood, upon which life depended, is ended. But before the circulation 

 of the blood ceases entirely in the lungs, the air which is mixed with 

 the blood escapes from the interstices, collects, grows rarefied, is 

 pumped to the brain, causes obstructions here and there; hence comes 

 the disorganized secretion of animal spirits in the brain, and hence 

 their irregular influence upon the muscles of the body, which is the 

 cause of the convulsions, and delays death. I do not doubt that all 

 animals whose heart has two ventricles and is not pierced by an oval 

 hole would die in a vacuum with the symptoms which I have re- 

 ported . . . 



The animals which have an oval hole opened in the heart live a 

 long time in a vacuum, and die only because of thirst, hunger, etc. 

 (P. 55.) 



And so, in the opinion of the celebrated professor of Leyden, 

 the death of animals subjected to a vacuum occurred as a result of 

 a stoppage of the circulation of the blood, a stoppage due to the 

 collapse of the lungs from which the vacuum had removed all the 

 air; furthermore, the gases which escaped from the blood ob- 

 structed the vessels, especially in the brain: 



They say (adds Musschenbroeck) that birds endure rarefied air 

 more easily and with less inconvenience than land animals, because 

 they are used to breathing a rarer air when they fly high: however, 

 they cannot endure an air three-quarters rarefied; that is why they 

 can rise only to a certain height in the atmosphere and not to all 

 kinds of heights: these animals are uneasy in a rarer air, because this 

 air can hardly, by its elasticity, expand the vesicles of the lungs unless 

 the chest is expanded by very great force; and this is the cause of the 

 uneasiness felt by the men who have climbed to the summits of the 

 high mountains of Armenia, Savoy, the Pyrenees, and Teneriffe, where 

 the air is much rarer than that which is near the surface of the earth. 

 (P. 57.) 



In France, the Academy of Sciences thought at first of making 

 experiments with "the machine of M. Guericke of Magdebourg"; 

 but the only one which its Memoirs 5 have reported to us dealt 

 with a gudgeon which, after the action of the vacuum, fell to the 

 bottom of the water, "its bladder being emptied". 



However, in England, one of the most remarkable experiment- 

 ing physicists of the seventeenth century, Robert Boyle, 6 had 

 undertaken very interesting researches on the life of animals sub- 

 jected to a vacuum. He used the pneumatic pump. His experi- 

 ments, published in 1670 in the Philosophical Transactions, surely 

 antedate this epoch considerably since some of them are quoted in 



