AND MARSHY SITUATIONS. 133 



Mr. Vanbreda's experiments, prove th:it there is Icfs 

 oxygen in the atmolphere ot marihes during autinnn 

 \' lien the weather is dry and hot, than in more falutary 

 fituations, and it is well known from innumerable ex- 

 periments made by different philofophcrs, that this can 

 only be diminifhed by combufi:ion, fermentation putre- 

 fadlion or refpiration, or a procefs of a fimilar kind. 



It is alfo a fa£l fully eftabliflied, that the fundions 

 of life as well as the proceis of combuftion and fermenta- 

 tion can only be continued by the application of oxy- 

 genous gas, and that thefe are afFeded in proportion to 

 the quantity and purity of the gas applied. 



It was formerly difcovered by Vefalius, and has fince 

 been confirmed by the obfervations of Drs. Lower, Prieft- 

 ley, ( raw ford and others, that the blood in the pulmonary 

 veins is of as red and florid a colour as in the arteries, 

 which is the reverfe in every other part of the fyftem. 

 This circumftance has been demonllratively proved to 

 be owing to the aftion of the oxygen, or the bafe of pure 

 air upon the blood in the pulmonary veins. 



From the experiments of the difcerning and ingenious 

 Dr. Goodwin upon living animals, it appears, that the 

 adlion of the heart cannot be continued by the reception 

 of blood, which has not undergone this change of colour 

 in the pulmonary veins from the application or intro- 

 duction of oxygen. This fadt has been fmce confirmed 

 by the experiments of Dr. Girtanner, as may be feen in 

 his Eflay on the principle and laws of irritability. 



That blood impregnated with oxygen, or the bafe of 

 pure air is the neceflary, and appropriate ftimulus for 

 giving motion to the heart, and enabling it to carry on the 

 circulation of the blood was rendered evident from the 

 gradual diminution and debility of its contra£tions, as the 

 colour of the blood became darker when the pure air was 

 excluded, and from its contradions becoming ftronger 

 S as 



