VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 325 



a striking example of the necessity of faithful experiments; by them alone we 

 can add certainty to science, and develope nature in her most secret and abstruse 

 operations; and as she is unchangeable in herself, every discovery extorted from 

 her is immutable. For want of attention to this laborious but sole method of 

 coming at truth, it is a pretty general opinion in the world, that even rotten ve- 

 getables are little noxious: and a late author, in a chapter on putrid fevers and 

 infection, expressly says : " The effluvia of rotten vegetable matters have little 

 effect in contaminating the air; from some experiments it appears, that they 

 possess rather an antiseptic virtue." We know however, by fatal experience, 

 that both animal and vegetable substances, when in a corrupted state, are the 

 obvious sources of the most dreadful and alarming diseases, from the mildest 

 putrid fever up to the plague itself. Sir John Pringle gives an instance of the 

 gaol or hospital fever, caused by the infection of a gangrened limb. A dreadful 

 fever was caused at Venice by a quantity of corrupted fish ; and at Delft by putrid 

 cabbages and other vegetables. Many instances of this kind may be brought, 

 by which countries have been almost depopulated. But it is no wonder that 

 animal and vegetable matter, when in a state of absolute corruption, should be 

 pregnant with such dreadful effects. Instinct leads us to fly from the danger 

 when we perceive the cadaverous smell. 



The Qth, 10th, J 2th, and 13th experiments demonstrate, that our senses are 

 by no means capable of distinguishing infection, nor, by warning us of the 

 danger, of leading us to avoid it. They show, that both animal and vegetable 

 matter, when perfectly fresh, sweet, and devoid of putrescency, exhales some- 

 what of a very noxious nature, inducing a putrid state in the living body, which 

 proves destructive to animal life. Hence in gaols, hospitals, and other crowded 

 places, we ought not by any means to estimate their wholesomeness by the ab- 

 sence of disagreeable smells alone. The principle of disease may lurk there 

 unperceived by our limited senses. The method used in these experiments is 

 the only true one by which we may judge with some degree of safety. 



The crowding together of a number of men in camps, hospitals, gaols, sick 

 rooms, &c. will presently generate a most malignant and infectious fever; and 

 in a very short time, especially if the place be close, unventilated, and the wea- 

 ther hot, the most fatal effects will follow. Of this we have a most remarkable 

 example in the affair at Calcutta, when 146 people, in perfect health, were, by 

 the effects of animal effluvia in a close and unventilated place, in the space of 

 eleven hours, all destroyed except 23, and those in a high, putrid fever, of 

 which however, by fresh air, &c. they gradually recovered. In all confined 

 places, ui proportion to their airiness, we find more or less of this. In hos- 

 pitals, though the wards may give no marks of it by any apparent dirtiness or 

 disagreeable smell, we may observe its effects ; diseases which usually admit in 



