84 POPtJLAR ERRORS. 



to them, have now yielded to more enlightened views, and are wholly 

 discarded from the consideration of the scientific physician, although 

 they still keep their hold upon the public mind, and form the main 

 instrument of that profitable delusion, by which, the empyric works 

 upon the credulity of the sick. In exposing the fallacy of the opinion 

 it may be sufficient to state at present, that whilst it is wholly assumed 

 as an hypothesis, it is contradicted by every fact which the research of 

 science has revealed to us. In no disease does the blood when drawn 

 from the arm, exhibit any material change in the nature and propor- 

 tion of its constituent principles, as existing in health, nor do the 

 remedies successfully employed for removing the disease, possess any 

 power to alter the condition of the blood. Besides the disorder, 

 which is hypothetically assumed to arise from an impurity of blood, 

 is often removed by the taking away of only a small quantity of this 

 fluid, and, at other times, as suddenly by other means, and, without 

 the possibility of the remedies having any power to subdue the imputed 

 cause, or relieve the efifect of it. To those who may not have well 

 considered the subject, it might appear a reasonable conclusion, that 

 as the solids of the body are made yVom the blood, and maintained by 

 it, that any disease occurring in the solids must proceed from the blood ; 

 but the answer to this ig plain ; for although the solids are formed 

 from the blood, it is hy the solids, that the blood itself is foiined ; 

 and before, therefore, any impurity can be generated in the blood, 

 there must be a derangement in the organs engaged in producing that 

 fluid ; and this derangement is disease ; and as it must precede any 

 change assumed to occur in the blood, it may exist without it ; and in 

 the absence of every fact to waiTant the contrary' notion, we may 

 certainly assume, that disease in all its forms, and through all its 

 changes, is, as its primary seat essentially limited to the solids. 

 But akin to this notion of a general impurity of the blood, and 

 as a material support to it,- is the importance attached by the 

 multitude to the appearance of the blood which is drawn from a 

 part by leeches. In some cases the blood disgorged from them 

 is black, and the conclusion thence deduced is that it is impure^ 

 and was partially stagnant in the part whence it was taken ; and 

 that the necessity for their use, and the benefit to be derived from 

 them, are to be measured by the colour of the blood. The notion, 

 however, with all its vagueness was taught and believed before the 



