AND IN EPIDEMICS. 71 



more or less soiled with earth. It is, also, in its most 

 hazardous condition, covered with dew, and is infected by 

 insects, and the seeds of various plants and flowers. 



Of these, the soil cannot give the venom, as it would 

 not lose such a power by the action of the plough. A 

 mineral poison would also be easily detected in it, and 

 could not propagate itself through a succession of animals; 

 nor has it a reproductive power. 



We are reduced, therefore, to the only remaining hypo- 

 thesis, the introduction of an organic poison of some kind, 

 animal or vegetable, into the nostrils or stomachs, (proba- 

 bly the latter,) of the affected animals. The long latent 

 continuance of the poison in the body, the apparently small 

 quantity of it necessary to create disease, and the seeming 

 reproduction after reception, all enforce the conviction 

 that the virus is organic. 



Having rendered probable the presence, in these cases, 

 of an organic agent, the usual course of medical reasoning 

 would lead us to assume its animal derivation, especially 

 as it seems to have, even in the system, a reproductive 

 power. But just at this point of time, the microscopic 

 discovery of the frequent connection of vegetations with 

 cutaneous and mucous diseases, and the probability that, 

 in other, and somewhat analogous cases, cryptogamous 

 plants exercise a disease-creating power, embarrass us with 

 a new element of difficulty. 



Animal poisons are usually soluble, are commonly in- 

 nocuous in the stomach, are not most potent at night, do 

 not affect particularly the autumnal season; nor can we 

 see how the plough could correct the evil, if of an animal 

 character. The extraordinary fixity and indestructibility 

 of the germs of this disease, point strongly to a vegetable 

 source. 



