MICROORGANISMS AND HUMAN WELFARE 29 



however, if the citizens insisted that the streets be kept 

 watered, especially when they are swept. Street sweeping 

 and the removal of garbage should be done as far as possible 

 at night. 



25. Treatment of cuts. A vast amount of discomfort 

 and possible danger from bacterial infection in the body 

 would be avoided if people but used proper care in the treat- 

 ment of wounds. We have seen that white corpuscles 

 resemble amcebse in their structure and activities (7). Let 

 us now study their functions 

 in the human body. When 

 one gets a sliver of wood in 

 one's finger and leaves it there 

 for a time, the finger becomes 

 more or less swollen and sore, 

 and white " matter " or pus 

 usually forms in the region of 

 the wound. These effects are 

 principally due to the activity 



Of bacteria, Which Were Car- 6 ^ ia white corpuscle destroyed by bac- 



ried into the wound on the 



piece of wood. Finding in the tissues all the favorable 



conditions for growth, these minute organisms multiply 



rapidly and produce poisons called toxins, that cause the 



inflammation. 



As soon however, as these inflammatory processes begin, 

 large numbers of white corpuscles are hurried to the spot 

 and proceed to attack the invading bacteria. If the number 

 of germs is relatively small, and if the corpuscles are in a 

 healthy condition, these cells of the blood seize upon and 

 devour the bacteria (Fig. 12) in the same way that an amoeba 

 takes in its food. Under these conditions little if any 



FIG. 12. White corpuscles. 

 a = a white corpuscle devouring a bao- 



