228 Medicine. 



gress j and they likewise constitute the basis of the 

 principles which were afterwards so successfully 

 applied to explain the nature and objects of the 

 function of respiration. 



It is universally known, that the merit of taking 

 the lead in the application of the principles of 

 pneumatic chemistry to explain the function of the 

 lungs, is due to Dr. Priestley.'' In the year 1774* 

 he discovered the existence, and many of the pro- 

 perties, of oxygen. Mr. Scheele made the same 

 discovery nearly at the same time. Not long af-- 

 terwards these two philosophers demonstrated that 

 the quantity of oxygenous gas is diminished in 

 respiration. In 1776 Lavoisier proved that at- 

 mospheric air is compounded of oxygen and azote, 

 brought by means of caloric to the state of elastic 

 fluids. In the following year that eminent philoso- 

 pher discovered that a quantity of carbonic acid 

 gas is found in air after it has been respired for 

 some time, which did not previously exist in it, 

 Some time afterwards he found, by a variety of ex- 

 periments, that no animal can live in air totally 

 deprived of oxygen. This fact was soon confirmed 

 and extended by the experiments of many other 

 philosophers, who proved that even fishes, which 

 do not perceptibly respire, and frogs, which can 

 suspend their respiration at pleasure, speedily die 

 if the water in which they are placed becomes 

 destitute of oxygenous gas." 



By a further prosecution of observations and ex- 

 periments on this subject, it was not long after^ 

 wards satisfactorily established, that certain re- 

 markable changes are produced by respiration not 

 only upon the air respired, but likew^ise upon the 



z For a considerable portion of the facts detailed In several of the fol- 

 lowing paragraphs, on the subject of respiration^ the author is indebted to a 

 very respectable work, entitled, A System of Ctsmistry^ by Thomas 

 Thomson, M.D. 4 vols. 8vo. i8oz. 



« CaRRADORJ, Amu de Chim, xxix, 171. 



