' 244 DISEASES Clafs II. i. 6. o 



creafes the acrimony of the purulent matter, and even converts 

 it into a weaker kind of contagious matter ; that is, to a mate- 

 rial inducing fever. This was afcribed to the union of the azotic 

 part of the atmofphere with the effufed pus in Seel. "XXVIII. 2. 

 but by contemplating iricre numerous facts and analogies, I am 

 now induced to believe, that it is by the union of oxygen with it ; 

 firftjbecaufe oxygen fo greedily 'unites with other animalfubftances, 

 as the blood, that it will pafs through a moid bladder to combine 

 with it, according to the experiment of Dr. Prieftley. ' Secondly, 

 becauie the poifons of venomous creatures are fuppofed to be 

 acids of different kinds, and are probably formed by the contact 

 of air after their fecreticn. And laftly, becaufe the contagious 

 matter from other ulcers, as in itch, or fmall-pox, is formed oii 

 external membranes, and are probably combinations of animal 

 matter and oxygen, producing other new acids. 



Since having written the above, Dr. Mitchill, of New York, 

 has fpoken much of the feptic quality of azote, or nitrogen ; and 

 thinks that it is the union of this part of the atmofphere with 

 the matter of ulcers, which produces or increafes its contagious 

 cr fever-exciting property •, which I had myfelf at firfl: believed, 

 as mentioned in Part I. Seel: XXVIII. 2. In fupport of this 

 opinion, it may be faid, that proper ventilation with purer air is 

 believed certainly to diminifh or deflroy infection j as fpoken of 

 In Clafs II. It 3. where it is propofed to difengage oxygen from 

 manganefe, for the purpofe of purifying crowded apartments. 

 But further experiments muft determine this curious inquiry ; 

 which might be attended with important confequences, if azote, 

 and not oxygen, could be (hewn to prevent the healing of pul- 

 monary ulcers ; as oxygen might be refpired alone, or mixed 

 with hydrogen or with carbonic acid gas, inftead of with azote. 



It was thought a fubjecl of confequence by the -ZEfculapian 

 Society at Edinburgh, to find a criterion which mould diftin- 

 guifli pus from mucus, for the purpofe of more certainly dis- 

 covering the pretence of ulcers in pulmonary difeafes, or in 

 the urinary paffages. For this purpofe that fociety offer- 

 ed their firil gold medal, which was conferred on the late Mr. 

 Charles Darwin, in the year 1778, for his experiments on this 

 fubjecT:. From which he deduces the following conclufions : 



" 1. Pus and mucus are both foluble in the vitriolic acid, 

 though in very different proportions, pus being much the leis 

 ibluble. 



" 2. The addition of water to either of thefe compounds de- 



compofes it ; the mucus thus feparated, either fwims on the mix- 



tttfce, or forms large fibcci in it ; whereas the pus falls to the 



tettotnj and forms on agitation a uniform turbid mixture. 



* "3. Pus 





