ANATOMY AND PHYSIOLOGY 



from the lungs Dr. Priestley, as usual, being in the 

 van. His initial experiments were made in 1777, and 

 from the outset the problem was as good as solved. 

 Other experimenters confirmed his results in all their 

 essentials notably Scheele and Lavoisier and Spal- 

 lanzani and Davy. It was clearly established that 

 there is chemical action in the contact of the air with 

 the tissue of the lungs ; that some of the oxygen of the 

 air disappears, and that carbonic-acid gas is added to 

 the inspired air. It was shown, too, that the blood, 

 having come in contact with the air, is changed from 

 black to red in color. These essentials were not in dis- 

 pute from the first. But as to just what chemical 

 changes caused these results was the subject of contro- 

 versy. Whether, for example, oxygen is actually ab- 

 sorbed into the blood, or whether it merely unites with 

 carbon given off from the blood, was long in dispute. 

 Each of the main disputants was biased by his own 

 particular views as to the moot points of chemistry. 

 Lavoisier, for example, believed oxygen gas to be com- 

 posed of a metal oxygen combined with the alleged ele- 

 ment heat ; Dr. Priestley thought it a compound of pos- 

 itive electricity and phlogiston; and Humphry Davy, 

 when he entered the lists a little later, supposed it to 

 be a compound of oxygen and light. Such mistaken 

 notions naturally complicated matters and delayed a 

 complete understanding of the chemical processes of 

 respiration. It was some time, too, before the idea 

 gained acceptance that the most important chemical 

 changes do not occur in the lungs themselves, but in 

 the ultimate tissues. Indeed, the matter was not clear- 

 ly settled at the close of the century. Nevertheless, 



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