HAMILTON SCmwriFIC ASSOCIATION 43 



mouth. Many are removed with the saliva, which inhibits their 

 growth and weakens their poisonous properties. Others are elim- 

 inated during the process of mastication. When bacteria reach 

 the stomach they are readily destroyed by the gastric juice. 



Thus it is seen how many lines of defence a micro-organism 

 must overcome before a foothold is obtained within the human 

 system. 



Now let us imagine that a colony having overpowered the 

 outer guard has secured a foothold within the tissues of the in- » 

 dividual. Has the body exhausted its means of defence ? Examine 

 what happens. 



A person suffers a wound of the hand from some septic instru- 

 ment. Germs pass from the instrument to the exposed tissue and 

 immediately begin to grow. Perhaps the wound is not thoroughly 

 cleaned. It is bandaged and left undisturbed for twenty-four hours. 

 When next examined the hand and perhaps the arm is reddened, 

 swollen and painful— inflamed, we say. What does this inflam- 

 mation mean? 



Inflammation is a reactive process on the part of the tissues, 

 induced by some injurious agent. Interpreted this means that the 

 body reasons on this wise : ' ' Something has happened to the tis- 

 sues of my hand. There is there some irritating injurious agent. 

 I must make an investigation. If necessary, I'll send down a 

 squad of policemen to remove the offender ; or I'll turn on a 

 hydrant and flush out the intruder ; or I'll forward an increased 

 supply of antitoxin or antibacterial substance so that the invader 

 may be destroyed." Accordingly the blood vessels around the 

 wound are engorged with blood conveying to the part the serum 

 with which to bathe it, the white blood celled policemen to attack 

 and destroy the germs, and the antitoxin and antibacterial sub- 

 stance to render the overthrow complete. 



Or again : A germ of tuberculosis obtains a foothold in a sec- 

 tion of lung tissue. The same inflammatory reaction is organized 

 to remove and destroy the germ, but in addition the body says : 

 " We must build up a barrier around this diseased focus that the 



