U9 



THE ORIGIN OF NATURAL IMMUNITY TOWARDS 

 THE PUTREFACTIVE BACTERIA. 



By R. Greig Smith, D.Sc, Macleay Bacteriologist to the 



Society. 



Immunity towards the putrefactive bacteria, that normall}'- 

 inhabit the intestine, is but a part, although an important one, 

 of the whole subject of immunity. It is, as we shall see, inti- 

 mately related to natural immunity towards stray pathogenic 

 bacteria that may obtain access to the tissues of an animal. 

 This form of immunity is the first line of defence of the animal, 

 the second being the production of anti-toxines in response to 

 the presence, action or effect of micro-organisms that have 

 obtained a foothold in the tissues. Individuals, races and 

 genera of animals exhibit differences in their susceptibility 

 towards bacterial invasion, but this is a question subsidiary to 

 that of a general immunity such as all animals possess towards 

 the bacteria that normally inhabit the intestinal tract. It is 

 towards the elucidation of this general immunity that I bring 

 forward certain views which appear to me to be feasible and 

 worthy of consideration. 



There is a tendency among writers to consider immunity 

 against bacteria as being in some way bound up with enzyme 

 action, and perhaps Pfeiffer may be cited as holding the most 

 advanced views in this direction. But beyond expressing the 

 idea that the action is enzymic, little is brought forward to explain 

 how the enzymes may act, and probable analogies are rarely 

 quoted. Immunity against toxines appears to be of a definite 

 chemical nature in opposition to the indefinite action that is 

 generally associated with the name of enzyme. The combination 

 between the anti-toxine and toxine is like that which occurs when 

 an acid unites with a base. Many writers have emphasised this, 



