CHAPTER X. 



THE LESIONS INDUCED BY POISONS. 



Forms of Poisons. 



A POISON has been commonly considered to be a substance which 

 when introduced into the body from without is capable of inducing, by 

 means other than mechanical, pathological alterations of function or 

 structure, or both. But this conception of poisons as extraneous pre- 

 formed substances has recently been greatly modified. For it has been 

 learned that poisons may be formed within the body, either through the 

 action of micro-organisms upon its organic constituents or through the 

 metabolism of the body cells themselves. 



It is thus convenient in considering the lesions induced in the body 

 by poisons toxic lesions to place in one group those due to preformed 

 extraneous poisons exogenous poisons and in another group those due 

 to substances formed within the body endogenous poisons. 



It has furthermore been found convenient to make three classes of 

 the endogenous poisons. First, those which are formed under the in- 

 fluence of micro-organisms in the course of the acute infectious diseases 

 and whose effects are most appropriately studied in that connection. 

 These may be called endogenous poisons of infectious origin. Second, those 

 which are formed under the influence of micro-organisms in the gastro- 

 intestinal canal or elsewhere and absorbed into the body fluids. Third, 

 those which are formed by the metabolism of the body cells themselves. 



To endogenous poisoning induced by either of the latter two classes 

 of agents, the term auto-intoxication has been most commonly and most 

 appropriately applied. 



As we have already studied the toxic lesions of the infectious diseases, 

 we have only to consider here : 



First, the lesions induced by preformed or extraneous poison ex- 

 ogenous poisom ; and second, those due to the endogenous poisons which are 

 concerned in the so-called auto-intoxications. l 



1 The limitation of the term auto-intoxication as it is here used is adopted from Ifar- 

 tim, who has written most clearly and suggestively upon the subject. See Martins. 

 ' Pathogenese innerer Krankheiten, " Heft 1 and 2, 1899-1900. 



