16 THEORIES ^ 



nent colleague. Professor Dunglison, in his work on Hy- 

 giene, ably exposes the fallacy of the received opinions on 

 this subject. He is not favorably impressed, indeed, by 

 any of the many hypotheses with which an obscure, but 

 highly important subject like this, is sure to be loaded. 



Not less antagonistic^ the received theory, is my friend, 

 Dr. John Bell, who, however ingenious and Jearned in his 

 opposition to it, does not also arrive at a negative conclusion, 

 but refers the morbid phenomena to the modification of 

 the sensible or appreciable conditions of the atmosphere. 

 His paper, contained in the Medical and Physical Journal, 

 for 1825, 1826, pp. 274-316, is worthy of an attentive 

 perusal, although written at a very early period of his 

 medical life. 



Notwithstanding, therefore, the seeming supererogation, 

 my duty as a teacher compels me to offer to you at least 

 a summary of the objections to current opinions on this 

 subject. 



The most forcible argument against the vegeto-aerial 

 theory, consists in the extraordinary exemption from ma- 

 larious diseases of places which, were it true, could not 

 escape a severe infliction. It is the more forcible, because 

 the theory is founded mainly upon the concurrence of such 

 diseases with heat, moisture and vegetation. If, then, it 

 can be shown that the alleged conditions exist in the most 

 perfect state, in very many places, without morbid results, 

 the universality of the coincidence can no longer be brought 

 to sustain the opinion. 



Again, if many places can be cited, where these sup- 

 posed elements are not at work, which are nevertheless 

 noted for their insalubrity, the opinion becomes even less 

 tenable. It is still farther weakened by the fact, often 

 observed, that under precisely the same apparent circum- 



