THE PLAGUE. Ill 



totally disabled, to the original encampment. We can 

 understand now, how, in the Odinka Hospital, whose sa- 

 lubrity was previously proved by the absence of cholera 

 during an epidemic at St. Petersburgh, its eight hundred 

 inmates continued in their usual health, despite the intro- 

 duction from without of five hundred cases of cholera. 

 We can see how a corps, in its march through an irregu- 

 larly infected country, may acquire and lose the cholera 

 several times; how a healthy corps may enter a sickly 

 army, en route, and not suffer from the prevailing malady. 

 The diffusion, the limitation, the leaving the infection be- 

 hind, or the carrying it forward, all admit of an easy ex- 

 planation, if we assume the hypothesis that germs or spores, 

 created exteriorly to the body, are the seminia morbi, 

 and that they are liable to the usual accidents by which 

 seeds are conveyed, or lost, or favored or repressed. 



It would now weary you, my young friends, were I to 

 carry you over the same twice-trodden ground, in an en- 

 deavor to apply to the phenomena of the origination and 

 propagation of THE PLAGUE, the same explanatory theory. 

 It fits it quite as well, nay, in some respects even more 

 perfectly than it does the etiology of cholera and yellow 

 fever, but, after what has been said, you can yourselves 

 make the application. 



In pursuit of our task of explanation, I am bound to f ' 

 give a reason for the extraordinary exemption of Brazil^- , 

 New Holland, and the Polynesian Islands, from malarious } 

 diseases. They are volcanic, or organic, or alluvial. They 

 have rank vegetation, and heat and moisture, as demanded 

 by McCulloch, and sulphur-products as called for by Daniel 

 and Gardiner, and a soil in process of drying after being 

 wet, as suggested by Ferguson. They have the exuber- 

 ance of vegeto-organic life of Armstrong and Doughty, 



