2-2{) HISTORY or 



also that deal in the preparations of metals of all kinds, are al- 

 ways unwholesome ; and the workmen, after some time, are ge- 

 nerally seen to labour under palsies, and other nervous con^ 

 plaints. The vapours from some vegetable substances are well 

 known to be attended with dangerous effects. The shade of the 

 manchineel tree, in America, is said to be fatal, as was that of 

 the juniper, if we may credit the ancients. Those who walk 

 through fields of poppies, or in any manner prepare those flowers 

 for making opium, are very sensibly affected with the drowsiness 

 they occasion. A physician of Mr Boyle's acquaintance, caus- 

 ing a large quantity of black hellebore to be pounded in a mor- 

 tar, most of the persons who were in the room, and especially 

 the person who pounded it, were purged by it, and some of them 

 strongly. He also gathered a certain plant in Ireland, which the 

 person who beat it in a mortar, and the physician who was 

 standing near, were so strongly affected by, that their hands and 

 faces swelled to an enormous size, and continued tumid for a 

 long time after. 



But neither mineral nor vegetable steams are so dangerous to 

 the constitution, as those proceeding from animal substances, 

 putrefying either by disease or death. The effluvia that comes 

 from diseased bodies, propagate that frightful catalogue of dis- 

 orders which are called infectious. The parts which compose 

 vegetable vapours and mineral exhalations, seem gross and heavy, 

 in comparison of these volatile vapours, that go to great dis- 

 tances, and have been described as spreading desolation over the 

 whole earth. They fly every where ; penetrate every where ; 

 and the vapours that fly from a single disease, soon render it 

 epidemic. 



The plague is the first upon the list in this class of human 

 calamities. From whence this scourge of man's presumption 

 may have its beginning, is not well known : but we well know 

 that it is propagated by infection. Whatever be the general 

 state of the atmosphere, we learn from experience, that the no- 

 xious vapours, though but singly introduced at first, taint the air 

 by degrees ; every person infected tends to add to the growing 

 malignity ; and as the disorder becomes more general, the pu- 

 trescence of the air becomes more noxious, so that the symptoms 

 are aggravated by continuance. When it is said that tlie origiw 

 of this disorder is unknown, it implies, that the air seems to be 



