3>^2 Sir Rickman John Godlee [March 12, 



extent that appears alarming. But again, as tlie air is effectually 

 filtered on the way, decomposition does not occur and the evil result 

 is only a temporary mechanical one. 



Investigators, therefore, began to think that the cause of fermen- 

 tation must be something solid and possil)ly living ; something so 

 small that it eluded their highest magnifying glasses, and so they 

 adopted different lines of attack. 



Some calcined the air, some filtered it, some passed it through 

 caustic fluids. Tliere was an old French confectioner named Apperfc 

 — Citoyen Appert, in the time of the Republic, who anticipated by 

 many years the work of our modern fruit preservers. He succeeded 

 in preserving all sorts of food in well-corked l:)ottles by boiling them 

 for various lengths of time according to the particular article he was 

 dealing with ; and his results were so nearly uniform and so remark- 

 able, from an economic as well as from a scientific point of view, 

 that they attracted the attention of the French ]\Iinister of the 

 Interior in 1810, and also of the Academic Frangaise. 



Unscientific as these observations were, they gave au impetus to 

 the work of chemists and biologists, who carried out an enormous 

 number of really scientific investigations in consequence. These 

 were repeated by Pasteur, who made countless others of his own, of 

 marvellous ingenuity. The results of his labours in this particular 

 field before 1865 may be given in a tabular form. He showed 

 that :— 



1. Putrefaction is a species of fermentation. 



2. It is caused by the growth of micro-organisms and does not 

 occur independently of them. 



3. The micro-organisms that produce fermentation and putrefac- 

 tion ai'e conveyed by the air on the dust that floats in it. 



4. These micro-organisms can be destroyed by heat and other 

 agencies, or separated by filtration. 



5. Certain recognizable organisms produce definite and distinct 

 fermentative processes. 



G. All of these organisms require oxygen. Some of them flourish 

 only in the presence of free oxygen (aerobic), others only in its 

 absence (anaerobic). The latter acquire their oxygen from the bodies 

 which, by their growth, they are causing to ferment or putrefy. 



7. Many natm-al animal and vegetable products have no tendency 

 to ferment or putrefy even in the presence of oxygen, if collected 

 with proper precautions and kept in sterilized vessels. 



8. Spontaneous generation has never been observed to occur, and 

 thus may be regarded as a chimera. 



Now it will be observed that Pasteur's work presented Lister with 

 two great fundamental facts : — 



1. That putrefaction is caused by germs which can be destroyed 

 by heat and chemicals and separated by filtration. 



2. That srerms are carried bv the dust in tlie air. 



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