1877.] 



Putrefactive and Infective Organisms. 



229 



Infusions of the substances above referred to were afterwards exposed 

 in succession to air which had been freed of its floating matter by filtra- 

 tion through cotton wool, also to air from which the floating matter had 

 been removed by calcination, and finally to vacua obtained by exhaustiug 

 as far as possible with an air-pump large receivers which had been 

 previously filled with filtered air. 



Boiled for five minutes and exposed to air thus treated, or to vacua 

 thus produced, none of the infusious showed subsequently any alteration 

 of colour or transparency to the naked eye, or to the microscope any 

 manifestation of life. 



Thus far I have summed up the results obtained with self -purified air, 

 filtered air, calcined air, and air-pump vacua, the liquids in all cases 

 being exposed in open test-tubes. Small retort-flasks were afterwards 

 resorted to. Charged with the infusions, they were boiled in heated oil 

 or brine, and sealed with exceeding care during ebullition. At the Royal 

 Society on January 13th, 1876, one hundred and thirty such flasks were 

 submitted to the Fellows, free alike from putrefaction and from life. 

 They embraced specimens of all the substances above mentioned and 

 some others. 



Briefly expressed, then, the evidence furnished by six months' assiduous 

 work during the autumn, winter, and spring of 1875-76, proved 

 conclusively that in the atmospheric conditions then existing in the 

 laboratory of the Eoyal Institution, not one of the many hundred flasks 

 and tubes experimented on failed to be sterilized by five minutes' boiling, 

 and no countenance was given to the notion that any of these once 

 sterilized infusions possessed the power of spontaneously generating life. 



The investigation embodied in the memoir now submitted to the 

 Society was opened in the summer of 1876 by a series of tentative ex- 

 periments on turnip infusions, to which were added varying quantities of 

 bruised or pounded cheese. Seven different kinds of cheese were 

 employed, fifty-seven test-tubes being charged with the mixture • and 

 exposed to the self -purified air of closed chambers. 



The majority of these mixtures remained unchanged ; a minority 

 became charged with organisms, which are, in my opinion, completely 

 accounted for by reference to the protective action of the cheese. In the 

 memoir of which this is an abstract such protective action is illustrated 

 by the fact that when ordinary mustard seeds were tied together in a calico 

 bag, they resisted the boiling temperature for a considerable multiple of 

 the time which sufficed to kill them when no bag enveloped them. The 

 bag and outside seeds protected the interior ones. 



Not temperature alone, but the ability to diffuse its juices or salts, 

 appears to be a condition of importance in the destruction of the integrity 

 and life of a germ by boiling water. Without diffusion a germ may 

 withstand temperatures competent to destroy it where diffusion is free. 



