Phenomena of Putrefaction and Infection. 67 



until they come, not only within range o£ the microscope, but 

 within range of the unaided senses. Let it be assumed that our 

 knowledge of them under these circumstances remains as defective 

 as it is now — that we do not know whether they are germs, 

 particles of dead organic dust, or particles of mineral matter. 

 Suppose a vessel (say a flower-pot) to be at hand filled with nutri- 

 tious earth, with which we mix our unknown particles, and that 

 in forty-eight hours subsequently buds and blades of well-defined 

 cresses and grasses appear above the soil. Suppose the experiment 

 when repeated over and over again to yield the same unvarying 

 result. What would be our conclusion ? Should we regard those 

 living plants as the products of dead dust or mineral particles, or 

 should we regard them as the offspring of living seeds ? The reply 

 is unavoidable. "We should undoubtedly consider the experiment 

 with the flower-pot as clearing up our preexisting ignorance ; we 

 should regard the fact of their producing cresses and grasses as 

 proof positive that the particles sown in the earth of the pot were 

 the seeds of the plants which have grown from them. It would 

 be simply monstrous to conclude that they had been " sponta- 

 neously generated." 



This reasoning applies word for word to the development of 

 Bacteria from that floating matter which the electric beam reveals 

 in the air, and in the absence of which no Bacterial life has been 

 generated. There seems no flaw in this reasoning ; and it is so 

 simple as to render it unlikely that the notion of Bacterial life de- 

 veloped from dead dust can ever gain currency among the members 

 of a great scientific profession. 



A novel mode of experiment has been here pursued, and it may 

 be urged that the conditions laid down by other investigators in 

 this field, which have led to different results, have not been strictly 

 adhered to. To secure accuracy in relation to these differences, the 

 latest words of a writer on this question, who has materially in- 

 fluenced medical thought both in this country and in America, are 

 quoted. " We know," he says, " that boiled turnip- or hay-infu- 

 sions exposed to ordinary air, exposed to filtered air, to calcined air, 

 or shut off altogether from contact with air, are more or less prone 

 to swarm with Bacteria and Vibriones in the course of from two 

 to six days." Who the " we" are who possess this knowledge is 

 not stated. The author is certainly not among the number, 

 though he has sought anxiously for knowledge of the kind. lie 

 thus tests the statements in succession. 



And first, with regard to filtered air. A group of twelve large 

 test-tubes was caused to pass air-tight through a slab of wood. The 

 wood was coated with cement, in which, while hot, a heated " pro- 

 pagating-glass " resembling a large bell-jar was imbedded. The air 

 within the jar was pumped out several times, air filtered through 

 a plug of cotton-wool being permitted to supply its place. The 

 test-tubes contained infusions of hay, turnip, beef, and mutton — 

 three of each, twelve in all. They are as clear and cloudless at 

 the present moment as they were upon the day of their introduc- 



F2 



