PARASITIC BACTERIA. 155 



But while we recognise this uncertainty in the de- 

 tails, we may be assured of the general facts. 

 The living body has some very efficacious resist- 

 ant forces which prevent most bacteria from 

 growing within its tissues, and which in large 

 measure may be relied upon to drive out the true 

 pathogenic bacteria. These resistant forces are 

 in part associated with the productions of body 

 poisons, and are in part associated with the active 

 powers of special cells which have been called 

 phagocytes. The origin of the poisons and the 

 exact method of action of the phagocytes we may 

 well leave to the future to explain. 



These resisting powers of the body will vary 

 with conditions. It is evident that they are 

 natural powers, and they will doubtless vary with 

 the general condition of vigour of the individual. 

 Robust health, a body whose powers are strong, 

 well nourished, and vigorous, will plainly furnish 

 the conditions for the greatest resistance to bac- 

 terial diseases. One whose bodily activities are 

 weakened by poor nutrition can offer less resist- 

 ance. The question whether one shall suffer 

 from a germ disease is not simply the question 

 whether he shall be exposed, or even the question 

 whether the bacteria shall find entrance into his 

 body. It is equally dependent upon whether he 

 has the bodily vigour to produce alexinesin proper 

 quantity, or to summon the phagocytes in suffi- 

 cient abundance and vigour to ward off the attack. 

 We may do much to prevent disease by sanitation, 

 which aids in protecting the individual from at- 

 tack ; but we must not forget that the other half 

 of the battle is of equal importance, and hence 

 we must do all we can to strengthen the resist- 

 ing forces of the organism. 



