150 The Story of the Bacteria 



harmless life. Along the digestive canal they 

 swarm. But these are mostly harmless, some 

 even lending a hand, perhaps, in reducing our 

 complex foods to simple forms. The tonsils 

 are rather weak points in the body armor, 

 for through them several objectionable germs, 

 among them the tubercle bacillus, sometimes 

 enter. 



When bacteria get into the real interior 

 for the lungs and bowels we may wisely 

 remember, are only infoldings from the ex- 

 terior when they get into the very tissue 

 itself, and into the blood, even then nothing 

 very startling happens, as a rule. The power 

 of the leucocytes and other cells to take up 

 dead stuff comes in handy here, for when the 

 average bacterium is encountered in the homes 

 of the leucocytes, it is either engulfed forth- 

 with or poisoned first and swallowed after- 

 wards (Plate XI., 3). 



It is only now and then with the very few 

 of the thousands of species of bacteria which 

 are co-inhabitors of the earth with us, that 

 difficulties arise. 



There are doubtless a good many interesting 



