INFECTION. 93 



"While a given, appreciable quantity of poison is necessary to 

 specific action, we find in infectious diseases the contrary to be the 

 case. "We can not appreciate the minuteness of the quantity of in- 

 fectious element necessary to produce an infectious disease. 



A single bacterium, in a condition of active proliferation, can lead 

 to the development of anthrax, if inoculated into a susceptible or- 

 ganism. 



Who would have temerity enough to introduce under his skin 

 even the smallest part of the point of the finest needle which had 

 been dipped in the saliva of a rabid dog? Yet we can neither weigh 

 nor otherwise appreciate the quantity of the inficieus introduced. 



You need no further proof of the impossibility of unformed 

 elements causing infection. Unformed elements have not the power 

 of self-multiplication. 



"We are, then, naturally driven to the assumption of organized 

 elements, as the etiological momenta in infection. 



The elements of infection must have the faculty of multiplica- 

 tion. They must have the faculty of taking up soluble nutriment 

 from their surroundings. 



"What, then, must be the real nature of these elements ? Our 

 studies and experiments have clearly shown that, of all organic life, 

 but one form has the characteristics which conform to these con- 

 ditions. That is the bacteria ; or, more particularly, the schizomy- 

 cetes, or fission, spore-producing fungi. 



These fungi correspond in every particular with our theories. 

 They are small enough to be taken up in numbers, under favorable 

 conditions, and widely dispersed by the atmospheric currents. They 

 possess the ability to multiply to an incredible degree, doubling their 

 numbers, under suitable conditions, in a few minutes. Their te- 

 nacity of life exceeds that of any known objects. 



While the essential characteristics of the bacteria in question so 

 fully conform to our hypothesis, our practical experiences are not so 

 full of assurance. 



While, in some few diseases — diphtheria, intermittent fever, an- 

 thrax, and emphysema infectiosum — we find the fission-fungi or 

 spores present in great numbers, in other hypothetic germ-diseases 

 they are frequently wanting, or very seldom met with. 



While we must admit the meagerness of our knowledge as to 

 the manne'r of life of these bacteria, yet we may assume that their 

 deleterious action extends itself in three directions. 



While the infectious elements act in the smallest quantities in 

 the purely contagious diseases, when introduced into a suitable or- 



