402 POISONS, CONTAGIONS, MIASMS. 



the fermentation of wort proceeded with the same 

 rapidity as that of the particles of the sugar con- 

 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 commencement 

 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 effects 

 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 manner 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 substan- 

 ces, which are absent from it in other stages of 

 growth. The susceptibility of contagion by peculiar 

 exciting bodies in childhood, indicates a propagation 

 and regeneration of the exciting bodies, in conse- 

 quence of the transformation of certain substances 

 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 transforma- 

 tions are perfected on constituents of the body which 

 are not essential to life, without the other parts 

 taking a share in the decomposition; it is termed 

 malignant when they affect essential organs. 



It cannot be supposed, that the different changes 

 in the blood, by which its constituents are converted 

 into fat, muscular fibre, substance of the brain and 

 nerves, bones, hair, &c., and the transformation of 

 .food into blood, can take place without the simulta- 



