and of Contagious Difeafcs. 183 



(low, continued, continual, dyfenteric, contagious or infec- 

 tious, according to the circumftances that may occur in the 

 progrefs of the difeafe. 



" The main difficulty left is to account for the cold fit of a 

 regular tertian. This ftage of fever I believe to depend 

 upon impeded refpiration, and the impeded refpiration to 

 depend upon the vitiated quality of the air taken into the 

 lungs ; or in fome (lighter cafes, where the ftomach n 

 originally thrown into a disordered ftate, the lungs, by affo- 

 ciation with that organ, are thrown into diforder too, and 

 for a time perform their functions but imperfectly. 



" Thus I prefume it is that the impeded (late of refpira- 

 tion is attended with a fmaller evolution of heat and oxygen 

 in the lungs, and consequently with more or lefs diminu- 

 tion in the? circulation of the blood, and a proportionable 

 degree of chillinefs and coldnefs throughout the body. The 

 duration and degree of the cold fit will correipond to the 

 continuance and power of the caufes disturbing the pulmonic 

 organs, either by acting upon them directly ( or indirectly 

 through the intermedium of the ftomach. 



" From the fmall quantity of heat and oxygen communi- 

 cated to the blood in the lungs, and the confequent flow 

 and feeble circulation of the blood, can the flirinking, pale- 

 nefs, tremors, coldnefs, debility, &c. &c. be fufficiently ex- 

 plained, as the conftitution is now deprived of its two chief 

 (timulants. 



" But why does not the continued operation of the vitiated 

 air upon the lungs, or the affociated condition of the lungs 

 with the ftomach, go on in an increafing Series even unto 

 death ? The power of our constitutions to become fami- 

 liarifed to the action of noxious caufes, is evinced by the 

 innocent operation of poifonous fubftances, which, by fre- 

 quent repetition, grow gradually habitual, and by cuftom 

 lofe their primary operation. This difpofition to becoae 

 familiarifed to vitiated airs, is apparent in the inhab tants of 

 Africa, who arc lo feafoned to the air and climate they live 

 N 4 in. 



