48o ON THE CAUSATION OF 



germ theory of putrefaction. These experiments of Schwann's appear to me 

 to prove conclusively that oxygen, as ordinarily understood by chemists, cannot 

 of itself occasion putrefaction. It is true, indeed, that, if you attempt to 

 repeat the experiments, you may meet with failure. But it must be remem- 

 bered that merely negative results go for nothing here, if the positive evidence 

 rests on satisfactory authority. This is a point which has been too little borne 

 in mind in the discussion of this subject. If we consider what the germ theory 

 assumes^ how minute the putrefactive particles are supposed to be, and how uni- 

 versally present in the atmosphere, and in the dust which adheres to all objects 

 exposed to it, it is easy to understand failure in such experiments consistently 

 with the truth of the theory. But it is impossible to understand success in 

 any single instance, consistently with the falsehood of the theory. If in any one 

 case it really happened that a decoction of meat remained without putrefac- 

 tion for weeks together, though freely exposed to air, unaltered, except by 

 having been temporarily subjected to a high temperature, this is enough to 

 show that oxygen, as known to chemists, is not the sole cause of the change 

 in question.^ One genuine successful experiment out of a thousand is enough 

 to establish that point. 



Schwann's observations, however, did not receive the attention which 

 they appear to me to have deserved. The fermentation of sugar was generally 

 allowed to be occasioned by the Torula Cerevisiae ; but it was not admitted 

 that putrefaction was due to an analogous agency. And yet the two cases 

 present a very striking parallel. In each a stable chemical compound, sugar 

 in the one case, albumen in the other, undergoes extraordinary chemical 

 changes under the influence of an excessively minute quantity of a substance 

 which, regarded chemically, we should suppose inert. As an example of this 

 in the case of putrefaction, let us take a circumstance often witnessed in the 

 treatment of large chronic abscesses. In order to guard against the access 

 of atmospheric air, we used to draw off the matter by means of a cannula and 

 trocar, such as you see here, consisting of a silver tube with a sharp-pointed 

 steel rod fitted into it, and projecting beyond it. The instrument, dipped 

 in oil, was thrust into the cavity of the abscess, the trocar was withdrawn, 

 and the pus flowed out through the cannula, care being taken by gentle pressure 

 over the part to prevent the possibihty of regurgitation. The cannula was then 

 drawn out with due precaution against the reflux of air. This method was 

 frequently successful as to its immediate object, the patient being relieved 



' Such experiments are peculiarly likely to fail in the hands of those who perform them with the 

 object of confuting the germ theory. In fact, a belief in the theory is almost essential in order that 

 the experimenter may be sufficiently keenly ahve to the subtle sources of failure 



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