360 POISONS, CONTAGIONS, MIASMS. 



may operate as a medicine, when it produces only 

 a partial change. 



No other component part of the organism can be 

 compared to the blood, in respect of the feeble 

 resistance which it offers to exterior influences. 

 The blood is not an organ which is formed, but an 

 organ in the act of formation ; indeed, it is the sum 

 of all the organs which are being formed. The 

 chemical force and the vital principle hold each 

 other in such perfect equilibrium, that every dis- 

 turbance, however trifling, or from whatever cause 

 it may proceed, effects a change in the blood. This 

 liquid possesses so little of permanence, that it can- 

 not be removed from the body without immediately 

 suffering a change, and cannot come in contact 

 with any organ in the body, without yielding to its 

 attraction. 



The slightest action of a chemical agent upon the 

 blood exercises an injurious influence ; even the 

 momentary contact with the air in the lungs, 

 although effected through the medium of cells and 

 membranes, alters the colour and other qualities of 

 the blood. Every chemical action propagates itself 

 through the mass of the blood ; for example, the 

 active chemical condition of the constituents of a 

 body undergoing decomposition, fermentation, pu- 

 trefaction, or decay, disturbs the equilibrium 

 between the chemical force and the vital principle 

 in the circulating fluid. The former obtains the 



