3*78 POISONS, CONTAGIONS, MIASMS. 



however, should be first decomposed, the gluten remaining- in so- 

 lution is not converted into yeast. We see, therefore, that the 

 reproduction of the exciting body or ferment here depends — 



1. Upon the presence of that substance from which it was 

 originally formed ; 



2. Upon the presence of a compound capable of being decom- 

 posed by contact with the exciting body. 



If we express in the same terms the reproduction of conta- 

 gious matter in contagious diseases, since it is quite certain that 

 they must have their origin in the blood, we must admit that the 

 blood of a healthy individual contains substances, by the decom- 

 position of which the exciting body or contagion can be produced. 

 It must further be admitted, when contagion results, that the 

 blood contains a second constituent capable of being decom- 

 posed by the exciting body. It is only in consequence of the 

 transformation of the second constituent, that the original exciting 

 body can be reproduced. 



A susceptibility of contagion indicates the presence of a 

 certain quantity of this second body in the blood of a healthy 

 individual. The susceptibility for the disease and its intensity 

 must augment according to the quantity of that body present in 

 the blood ; and in proportion to its diminution or disappearance, 

 the course of the disease will change. 



When a quantity, however small, of contagious matter, 

 that is of the exciting body, is introduced into the blood of a 

 healthy individual, it will be again generated in the blood, 

 just as yeast is reproduced from wort. Its condition of trans- 

 formation will be communicated to a constituent of the blood ; 

 and in consequence of the transformation suffered by this 

 substance, a body identical with or similar to the exciting or 

 contagious matter will be produced from another constituent 

 substance of the blood. The quantity of the exciting body 

 newly produced must constantly augment, if its further trans- 

 formation or decomposition p 'oceeds more slowly than that of 

 the compound in th* blood, the decomposition of which it 

 effects. 



If the transformation of the yeast generated in the fermen- 

 tation of wort proceeded with the same rapidity as that of the 



