and the Cause of Epidemic Disorders. 125 



more importance to the chemist than the solution of the pro- 

 blem, which may be stated in these terms — An effect being 

 given, to know the specific nature of the bodies which produce 

 it, and the circumstances in which they manifest themselves to 

 our observation. There are problems, belonging to this ge- 

 neral proposition which have been solved, when a compound 

 substance, endowed with strong influence upon the animal eco- 

 nomy, such as opium, cinchona, nux vomica, &c. being given, 

 Messrs Sertuerner, Duncan, BouUai, Pelletier, Caventou, &c. 

 have extracted from them their active principles. These 

 discoveries have so much of a chemical character about them, 

 that the spirit which made them cannot but direct the efforts 

 of analysis when applied to the inquiry concerning the dele- 

 terious substances which analogy leads us to presume exist in 

 the atmosphere, in water, and morbid secretions, &c. In re- 

 commending investigations of this sort, however, we cannot 

 too strongly insist upon the critical accuracy which must be 

 maintained throughout. It is not because a peculiar substance 

 has been found in an atmosphere which has been suspected to 

 be vitiated, or in water which is supposed to be prejudicial to 

 health, or that a peculiar proximate principle has been recog- 

 nised in morbific products, that we should attribute to this 

 body or principle, the cause we are in search of. Such a 

 conclusion can be allowed only where it shall have been 

 proved by a positive experiment that the effect whose cause 

 we wish to discover, is the result of the mutual action of this 

 body, and of a substance belonging to the animal economy ; for 

 it should never be forgotten that often in the animal ma- 

 chine a morbid principle, that is to say, a principle whose ele- 

 ments have been associated under the influence of some dis- 

 ease, may be perfectly harmless upon the animal frame, as is 

 the saccharine matter of Diabetes. Hence the presence of this 

 principle in the morbid matter which contains it, can only be 

 an index, a symptom, and not the cause of this disorder ; and 

 it is under this last point of view that the agglomerated mul- 

 berry and mucous globules should be considered in the milk 

 of cows attacked with the cocote, provided the probability Ave 

 now possess of the harmlessness of this milk becomes a cer- 

 tainty, by subsequent researches. 



