INTRODUCTION AND DEDICATION. V 



nation of that hypothesis on this side of the Atlantic ; so 

 that he is apparently entitled to the credit of having 

 made, if not a new, at least an original theory of the 

 cause of cholera. 



As you have heard these lectures, gentlemen, you may 

 not have forgotten that, in making my selection of facts 

 and observations, I have, with a single exception, studi- 

 ously avoided an appeal to phenomena perceived only by 

 myself. I have created no facts for this subject; because 

 I have long learned, as you will learn, to trust reservedly 

 to alleged truths observed by a theorist, who cannot avoid, 

 however just he may be, the coloring which, through a 

 blinding partiality for a new discovery or hypothesis, is 

 too often given. 



I have not, however, been idle. Experiments are in 

 progress which seem to promise more direct and unques- 

 tionable proof of the validity of our hypothesis ; but they 

 are yet incomplete, and therefore should not now appear, 

 lest they might load so young a conception with a too 

 dubious weight. 



As there may, in the future, arise some dispute respect- 

 ing the paternity of the theory which is now proposed, I 

 may be indulged with the liberty of quoting the follow- 

 ing extract from a letter by Professor J. W. Bailey, in 

 answer to one from me: 



" West Point, March 5th, 1845. 

 { ' DOCTOR J. K. MITCHELL : 



" My dear Sir : Please accept my thanks for your favor of the 29th ultimo. 

 I was interested in your letter on the fungous origin of fevers; and it ap- 

 pears to me that you make out a very strong case, and one which appears 

 more satisfactory than Liebig's somewhat vague ideas of ' communication 

 of motion,' being the cause of the propagation of contagious poisons, fer- 



