368 POISONS, CONTAGIONS, MIASMS. 



tained in it, both would simultaneously disappear 

 when the fermentation was completed. But yeast 

 requires a much longer time for decomposition than 

 sugar, so that after the latter has completely disap- 

 peared, there remains a much larger quantity of 

 yeast than existed in the fluid at the commcement 

 of the fermentation, yeast which is still in a state 

 of incessant progressive transformation, and there- 

 fore possessed of its peculiar property. 



The state of change or decomposition which 

 affects one particle of blood, is imparted to a second, 

 a third, and at last to all the particles of blood in 

 the whole body. It is communicated in like man- 

 ner to the blood of another individual, to that of 

 a third person, and so on or in other words, the 

 disease is excited in them also. 



It is quite certain that a number of peculiar sub- 

 stances exist in the blood of some men and animals, 

 which are absent from the blood of others. 



The blood of the same individual contains, in 

 childhood and youth, variable quantities of sub- 

 stances, which are absent from it in other stages of 

 growth. The susceptibility of contagion by peculiar 

 exciting bodies in childhood, indicates a propaga- 

 tion and regeneration of the exciting bodies, in 

 consequence of the transformation of certain sub- 

 stances which are present in the blood, and in the 

 absence of which no contagion could ensue. The 

 form of a disease is termed benignant, when the 

 transformations are perfected on constituents of the 



