DUST AND DISEASE. 301 



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, say, 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 oc- 

 curred, 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 perpetually 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 canula and trocar having 

 been lying exposed to the air, dust will have been deposited upon them, 

 and will be present in the angle between the trocar and the silver tube, 

 and in that protected situation will fail to be wiped off when the instru- 

 ment is thrust through the tissues. Thus when the trocar is withdrawn, 

 some portions of this dust will naturally remain upon the margin of the 

 canula, which is left projecting into the abscess, and nothing is more 

 likely than that some particles may fail to be washed off by the stream 

 of out-flowing pus, but may be dislodged when the tube is taken out, 

 and left behind in the cavity. The germ-theory tells us that these par- 



