138 Of the Dn^SALUBRITY of FLAT 



the fcurvy, while the flaves that lived principally on 

 vegetables, but breathed a confined nnpure air fell mife- 

 rable viclims to it. 



The remarkable cafe of the blue boy, defcribed by Dr. 

 Sand. fort of Leyden, furnilhes another ftriking example 

 of the importance ot oxygen in the prefervation of health 

 and life, as well as a confirmation of its being the caufe 

 of the red colour of tlie blood. 



In this boy, whofe Ikin was as blue as indigo, the aoita 

 communicated with both ventricles cf the heart, in con- 

 fequence of which the greateft part of the blood was im- 

 mediately propelled from the right ventricle into the 

 aorta, fo that very little pafled into the pulmonary artery 

 to be oxygenated. 



An opinion equally erroneous with that which has 

 lately prevailed refpe£ting the caufes of intermittent 

 fevers, &c. has alfo been delivered down from age to age, 

 refpe£ting the caufes of continued fevers of the nervous 

 or putrid kind. 



The do6lrine formerly taught refpeding thcfe, was 

 that they derived their exiftencefrom the effluvia of dead 

 and putrid animal fubftances : but from more recent and 

 accurate obfervations, it appears that the contagion by 

 which this kind of fever is produced as well as thofe 

 of a peffilential nature, is aKvays derived from the livmg 

 human body in confined and unventilated lituations, and 

 it is probable that the effluvia thus excreted, partake of 

 the quality of nitrogen gas, from their being rendered 

 harmlefs by a union with oxygen or the bafe of pure 

 air. 



It appears more than probable alfo from the hiftory 

 of the circumftances always prefent at the time febrile 

 contagion is generated, that it is rendered virulent and 

 powerful in proportion to the abfence or defe£l of 

 oxygen and the degree of heat to which the living body 



has 



