PUTREFACTION AND FERMENTATION 481 



from the mass of the accumulated fluid, and experiencing no inconvenience 

 from the operation. But the pus was pretty certain to reaccumulate in course 

 of time, and it became necessary again and again to repeat the process. And 

 unhappily there was no absolute security of immunity from bad consequences. 

 However carefully the procedure was conducted, it sometimes happened, even 

 though the puncture seemed healing by first intention, that feverish symptoms 

 declared themselves in the course of the first or second day, and, on inspecting 

 the seat of the abscess, the skin was perhaps seen to be red, implying the 

 presence of some cause of irritation, while a rapid reaccumulation of the fluid 

 was found to have occurred. Under these circumstances, it became necessary 

 to open the abscess by free incision, when a quantity, large in proportion to 

 the size of the abscess, sa}^ for example, a quart, of pus escaped, fetid from 

 putrefaction. Now, how had this change been brought about ? Without the 

 germ theory, I venture to say, no rational explanation of it could have been 

 given. It must have been caused by the introduction of something from 

 without. Inflammation of the punctured wound, even supposing it to have 

 occurred, would not explain the phenomenon. For mere inflammation, whether 

 acute or chronic, though it occasions the formation of pus, does not induce 

 putrefaction. The pus originally evacuated was perfectly sweet, and we know 

 of nothing to account for the alteration in its quality but the influence of 

 something derived from the external world. And what could that something 

 be ? The dipping of the instrument in oil, and the subsequent precautions, 

 prevented the entrance of oxygen. Or even if you allowed that a few atoms 

 of the gas did enter, it would be an extraordinary assumption to make that 

 these could in so short a time effect such changes in so large a mass of 

 albuminous material. Besides, the pyogenic membrane is abundantly supplied 

 with capillary vessels, through which arterial blood, rich in oxygen, is per- 

 petually flowing ; and there can be little doubt that the pus, before it was 

 evacuated at all, was liable to any action which the element might be disposed 

 to exert upon it. 



On the oxygen theory, then, the occurrence of putrefaction under these 

 circumstances is quite inexplicable. But if you admit the germ theory, the 

 difficulty vanishes at once. The cannula and trocar having been lying exposed 

 to the air, dust will have been deposited upon thorn, and will be present in 

 the angle between the trocar and the silver tube, and in tliat }n"otected situa- 

 tion will fail to be wiped off when the instrument is thrust tlu'ough the tissues. 

 Then when the trocar is withdrawn, some portions of this dust will naturally 

 remain upon the margin of the cannula, which is left projecting into the abscess, 

 and nothing is more likely than that some particles may fail to be washed oft" 



