386 POPULAR SCIENCE MONTHLY 



arrived at a fairly accurate conception of the important part played 

 by these particles in the processes of life. He recognized that the 

 substance embodied in these particles " formed only a part of the 

 atmosphere, that it was essential for burning, that it was essential for 

 all the chemical changes on which life depends, that it was absorbed 

 into the blood from the lungs, carried by the blood to the tissues, and 

 in the tissues was the pivot, the essential factor of the chemical changes 

 by which the vital activities of this or that tissue are manifested. It 

 was essential in muscle to the occurrence of muscular contractions, 

 it was essential in the brain to the development of animal spirits. 

 This great truth was reached at a time when the men of chemistry 

 were struggling with the spiritualistic fermentations of van Helmont 

 on the one hand, and with the material effervescences of Sylvius on the 

 other. It was reached by a young man of twenty-five years, who died 

 a few years afterwards." 3 



For nearly a hundred years this fundamental idea so skillfully 

 worked out lay practically dormant and no material progress was made 

 until, in the latter part of the eighteenth century, Priestley prepared 

 his dephlogisticated air and Lavoisier discovered oxygen. Then came 

 ■essentially a revival of Mayow's views concerning respiration, only with 

 a clearer understanding of the nature of the process. As stated by 

 Lavoisier and Laplace, "respiration is a combustion, slow it is true, 

 hut otherwise perfectly similar to the combustion of charcoal. It 

 takes place in the interior of the lung without giving rise to sensible 

 light because the matter of the fire (the caloric) as soon as it is set 

 free, is forthwith absorbed by the humidity of these organs. The heat 

 developed by this combustion is communicated to the blood which is 

 traversing the lungs and from the lungs is distributed over the whole 

 animal system." 4 



In this conception of so-called respiration the fundamental errors 

 as viewed from the standpoint of to-day are first: the idea that the 

 process deals solely with the combustion of carbon and secondly, that 

 the process is limited to the lungs where a hydrocarbonous fluid was 

 supposed to be secreted, i. e., from or through the tubes of the lungs. 

 Later, Lavoisier himself recognized that in this process of combustion 

 in the animal body hydrogen (discovered by Cavendish in 1781) was 

 likewise involved, and that water as well as carbon dioxide was a normal 

 product of the oxidation that is associated with respiration. Still 

 later, the Italian investigator, Spallanzani, through his experiments on 

 animals broadened the conceptions then prevailing by proving that the 

 individual tissues of the body, like the organism as a whole, respire, 

 i. &., that they consume oxygen and produce carbon dioxide. This 



8 Quoted from Sir Michael Foster, loc. tit., p. 198. 

 * Ibid., p. 249. 



