694 ^-^^ POPULAR SCIENCE MONTHLY. 



Dr. Roberts infallibly contained them. In the gentle movement of 

 the air to and fro as the temperature changed, or in 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 would fall into the infusion and 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 fertilization being so rare as Dr. Roberts found 

 it to be, is a proof of the care with which his experiments were con- 

 ducted. But he did find cases of fertilization after prolonged expos- 

 ure to the boiling temperature; and this caused him to come to the 

 conclusion that, under certain rare conditions, spontaneous generation 

 may occur. He also found that an alkalized hay-infusion was so diffi- 

 cult to sterilize that it was capable of withstanding the boiling tem- 

 perature for hours without losing its power of generating life. The 

 most careful experiments have been made with this infusion. Dr. 

 Roberts is certainly correct in assigning to it superior nutritive 

 power. 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. But, holding the notions he does, 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. RoUo 

 Russell ; at Heathfield Park, Miss Hamilton; at Greenwich Hospital, 

 Mr, Hirst ; at Kew, Dr. Hooker; and at the Crystal Palace, Mr. Price, 

 kindly took charge of infusions, every one of which became charged 

 with organisms. But to obtain more definite insight regarding the 

 diffusion of atmospheric germs, a square wooden tray was penetrated 

 with a hundred holes, into each of which was dropped a short test- 

 tube. On October 23d, thirty of these tubes were filled with an in- 

 fusion of hay, thirty-five with an infusion of turnips, and thirty-five 

 with an infusion of beef. The tubes, with their infusions, had been 

 previously boiled, ten at a time, in an oil-bath. One hundred circles 

 were marked on paper, so as to form a map of the tray, and every day 

 the state of each tube Avas registered upon the corresponding circle. 

 In the following description, the term "cloudy" is used to denote the 

 first stage of turbidity, distinct but not strong. The term " muddy " 

 is used to denote thick turbidity. 



One tube of the hundred was first singled out and rendered mud- 



