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various sanitary reports which have been recently issued from 

 the principal towns in the kingdom. 



Having established the existence in atmospheric air of a 

 substance in a state of rapid decomposition, capable of 

 inducing disease when introduced into the animal frame, 

 we will next endeavour to trace out the cause why disease, 

 evidently produced from malaria, is capable of assuming 

 various forms in different localities and at different seasons ; 

 and also the reason why stagnant drains, &c., should be a 

 source of disease at one period and not at another. 



We have already stated that the disease produced by 

 decomposing sausages differs materially from that communi- 

 cated from dissection wounds ; and it would require a person 

 to be very little versed in chemistry to see that the kind of 

 decomposition going on in the sausages was entirely different 

 from that in the putrid body. In the first the change is 

 described as a slight softening, in which the mixture becomes 

 lighter in colour, without the escape of any gas; whereas 

 in the body considerable quantities of gas escape, and the 

 substance becomes much darker. This difference in the kind 

 of decomposition, which undoubtedly causes the difference in 

 the character of disease, may arise from two causes; first, 

 from a greater number of chemical compounds acting upon 

 each other at the same time, or from a larger or smaller 

 portion of moisture. We may, indeed, consider the presence 

 of various quantities of moisture in organic compounds, or 

 the degree of dilution of organic solutions, to be one of the 

 principal causes which modifies the putrid decomposition of 

 all organized bodies ; for it is well known that when a certain 

 amount of moisture is extracted from flesh, either by evapo- 

 ration or the action of salt, this change is entirely arrested. 

 We also know that the addition of a third substance to 

 fermenting wort, namely, the bitter principle of the hop, has 

 the effect of preventing the formation of an oily compound, 



