27fJ ADDITIONAL NOTES ON CONTAGION. 



.As connected with the same subject, and illustrative of the condition of atmosphere 

 produced by the introduction of an infectious ferment, and the means of destroying the 

 noxious compound, I subjoin the following valuable communication from Dr. Samuel Bard, 

 the venerable and learned President of the College of Physicians and Surgeons in the 

 University of the State of New- York. 



Hyde Park, July 27, 180fl. 

 Dear Sir, 

 I have read, with great pleasure, your arrangement and explanation of contagious dis- 

 eases, and am, by your arguments, confirmed in the opinion of the agency of a ferment, 

 sui generis, in the propagation of contagious and infectious diseases. I use these terms 

 here indiscriminately: indeed, I believe the analogy between fermentation and its various 

 products, and the progress and fomes of contagious distempers, applies more closely, and 

 to a greater extent, than has been generally supposed. 



For instance : under certain circumstances of heat and moisture, all vegetable and 

 animal matters run into fermentation ; that of vegetables passes through the stages of 

 vinous and acetous to a species of putrefactive ; that of animals likewise has its stages, as 

 is evident in the fermentation of milk ; and its products differ conspicuously, according aa 

 flesh, fish, fat, blood, or eggs are the subjects of it. 



An increased degree of heat always increases the rapidity with which fermentation goes 

 on; and other circumstances of the atmosphere, a greater or less degree of moisture and 

 dryness, a violent storm, thunder and lightning, moonlight, and probably many other less 

 evident causes combining with the heat, variously change, hasteu, or retard the process of 

 fermentation, as every person conversant with these subjects well knows. 



Again, the different constitutions, (or, if you please, a certain predisposition in vegetable 

 and animal substances,) have the same effect in hastening, retarding, and variously modi- 

 fying the products of fermentation : thus rich vegetable juices readily assume, and stop 

 at, the vinous stage, and with difficulty can be made to go on to the acetous ; poor and 

 crude vegetable juices can hardly be arrested at the vinous stage, but run rapidly into 

 the acetous ; and cabbages, and all vegetables of that class, can hardly be made to produce 

 either wine or vinegar, but quickly run into a kind of putrefactive fermentation. Fish 

 putrefies more readily than jiesh ; and there is a great difference in this respect between 

 the flesh of different animals. 



AH these circumstances are hastened, rendered more certain, and variously modified, 

 by the addition of a ferment ; and, lastly, a certain degree of cold prevents all fermentation, 

 and stops it where it has already begun. So it is with infectious epidemics; certain i\c 





