FERMENTATION 293 



men are beginning to fully realize their truth. In the 

 domain of surgery the justice of Boyle's surmise has been 

 most strictly demonstrated. But we now pass the bounds 

 of surgery proper, and enter the domain of epidemic dis- 

 ease, including those fevers so sagaciously referred to by 

 Boyle. The most striking analogy between a contagium 

 and a ferment is to be found in the power of indefinite 

 self-multiplication possessed and exercised by both. You 

 know the exquisitely truthful figures regarding leaven em- 

 ployed in the Kew Testament. A particle hid in three 

 measures of meal leavens it all. A little leaven leaveneth 

 the whole lump. In a similar manner, a particle of con- 

 tagium spreads through the human body and may be so 

 multiplied as to strike down whole populations. Consider 

 the effect produced upon the system by a microscopic 

 quantity of the virus of smallpox. That virus is, to all 

 intents and purposes, a seed. It is sown as yeast is sown, 

 it grows and multiplies as yeast grows and multiplies, and 

 it always reproduces itself. To Pasteur we are indebted 

 for a series of masterly researches, wherein he exposes the 

 looseness and general baselessness of prevalent notions re- 

 garding the transmutation of one ferment into another. 

 He guards himself against saying it is impossible. The 

 true investigator is sparing in the use of this word, though 

 the use of it is unsparingly ascribed to him; but, as a 

 matter of fact, Pasteur has never been able to effect the 

 alleged transmutation, while he has been always able to 

 point out the open doorways through which the affirmers 

 of such transmutations had allowed error to march in 

 upon them.* 



* Those who wish for an illustration of the care necessary in these re- 

 searches, and of the carelessness with which they have in some cases been 



