MICROOBGANISMS 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. 



Fig. 12. 



- White corpuscles. 



25. Treatment of cuts. — A vast amount of discorafprt. 

 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 amoebae 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- 

 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 



a = a white corpuscle devouring a bac- 

 terium. 



b = a wiiite corpuscle destroyed by bac- 

 teria. 



