178 Prof. J. Tyndall on the [Jan. 13, 



an ordinary pipette up to about two thirds of its capacity with the 

 infusion to be examined. In the neck of the pipette he places a plug of 

 dry cotton-wool. He then hermetically seals the neck, and dips the bulb 

 into boiling water or hot oil, where he permits it to remain for the 

 requisite time. Here we have no disturbance from ebullition and no 

 loss by evaporation. The bulb is removed from the hot water and per- 

 mitted to cool. The sealed end of the neck is then filed off, the cotton- 

 wool alone interposing between the infusion and the atmosphere. 



The arrangement is beautiful, but it has one weak point. Cotton-wool 

 free from germs is not to be found, and the plug employed by Dr. 

 Roberts infallibly contained them. In the gentle movement of the air to 

 and fro, as the temperature changed, or by any shock, jar, or motion to 

 which the pipette might be subjected, we have certainly a cause sufficient 

 to detach a germ now and then from the cotton-wool which, falling 

 into the infusion, would produce its effect. Probably also condensation 

 occurred at times in the neck of the pipette, the water of condensation 

 carrying back from the cotton-wool the seeds of life. The fact of fertili- 

 zation being so rare as Dr. Eoberts found it to be, is a proof of the care 

 with which his experiments were conducted. But he did find cases of 

 fertilization after prolonged exposure to the boiling temperature; and 

 this caused him to come to the conclusion that under certain rare con- 

 ditions spontaneous generation may occur. He also found that an 

 alkalized hay-infusion was so difficult to sterilize that it was capable of 

 withstanding the boiling temperature for hours without losing its power 

 of generating life. The most careful experiments have been made with 

 this infusion. Dr. Eoberts is certainly correct in assigning to it superior 

 nutritive pow r er. But in the present inquiry five minutes' boiling sufficed 

 to completely sterilize the liquid. 



Summing up this portion of his inquiry, the author remarks that he 

 will hardly be charged with any desire to limit the power and potency of 

 matter in regard to life. But holding the notions he does upon this 

 point, it is all the more incumbent on him to affirm that, as far as 

 inquiry has hitherto penetrated, life has never been proved to appear 

 independently of antecedent life. 



Though the author had no reason to doubt the general diffusion of 

 germs in the atmosphere, he thought it desirable to place the point 

 beyond question. At Down Mr. Darwin and Mr. Francis Darwin, at 

 High Elms Sir John Lubbock, at Sherwood, near Tunbridge Wells, Mr. 

 Siemens, at Pembroke Lodge, Richmond Park, Mr. Rollo Russell, at 

 Heathfield Park Miss Hamilton, at Greenwich Hospital Mr. Hirst, at 

 Kew Dr. Hooker, and at the Crystal Pa ] ace Mr. Price kindly took charge 

 of infusions, every one of which was invaded, many by astounding swarms 

 of organisms. To obtain more definite insight regarding the diffusion of 

 atmospheric germs a square wooden tray was pierced with 100 holes, into 



