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nature of certain minute particles discovered to exist in the 

 blood, and which some held to be of the nature of Bacteria. 



Next we know from the experiments of Pasteur, about 

 which I have already spoken, that the air is full of infecting 

 particles. Is the healthy body affected by these Particles ? To 

 determine this point Burdon-Sanderson pumped a large quan- 

 tity of air through the cellular tissue of rabbits, which, 

 however, remained quite unaffected. 



He then injected a small quantity of water into the 

 Peritoneal cavity, but with negative results. Then he 

 injected water charged with Bacteria, bred in an innocent 

 soil. Water and Bacteria were all absorbed, and abundance 

 of the organisms were found in the blood vessels and lympha- 

 tics, but no harm resulted beyond that caused by the 

 plugging of the small arterioles by the masses of organisms. 



With these preliminary observations we may now 

 inquire into what is known of the relation of Bacteria to 

 disease. Two classes of diseases have been separately 

 studied from this point of view. First, disorders arising out 

 of wounds, which naturally come under the notice of the 

 Surgeon, and secondl}', general diseases, which belong more 

 strictly to the Physician. 



We know that wounds are prone sometimes to take on 

 an unhealthy appearance. The discharges become foetid, 

 and at the same time the patient begins to suffer from con- 

 stitutional symptoms, which frequently end in death. This 

 ailment is known as Pyaemia or Septicaemia, according to 

 whether local abscesses are formed or not. This state of things 

 is specially apt to arise if the patient is exposed to insani- 

 tary conditions, or if he is in proximity to other similar cases. 

 Sir Joseph Lister held that the first cause of this change 

 was putrefaction of the discharge, due to contamination from 

 the air. You recollect his experiments on milk, which 

 showed, among other things, that souring milk contains 

 a special organism which is rarely found except in and about 

 dairies, and to which he gave the name of Bacternm Lactis. 

 The outcome of 'these experiments was the establishment of 



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