40 GENERAL SCIENCE 



pletely eliminated from the death lists of Havana. So 

 marked has the control of germ diseases become in the pres- 

 ent generation that during the building of the Panama 

 Canal (completed in 1914) the health record there under 

 American management was better than in many % cities of 

 the United States. Under French management of the canal 

 in the earlier years, and likewise when the Panama Railroad 

 was built, the death lists numbered thousands 1 . 



Bacteria and protozoa that exist in or upon living plants 

 or animals are known as parasites. Those that live upon 

 dead or decaying organic matter are called saprophites 

 (sap'ro-fits). As result of the growth and multiplication 

 of these micro-organisms the tissues upon which they feed 

 are broken down. In the human system the waste products 

 of their activities seem to act as poisons (toxins), destroying 

 the protoplasm of the cells. The expenditure of bodily 

 energy on the part of living tissues in a battle against these 

 destructive agencies, and in the elimination of the excessive 

 wastes of the body, is indicated in a fevered state of the 

 patient. 



The body after having become infected seems to have the 

 power to produce products known as antitoxins. These 

 either neutralize the effects of the toxins, or stop the mul- 

 tiplication of the disease germs, or both. If these anti- 

 toxins are produced rapidly enough after a person is infected, 

 and in sufficient quantity, the patient recovers even from 

 the most severe attacks; if not, he is likely to die. At 

 times a patient surviving the cycle of life changes of the 

 first of the germs has a " relapse," and a recurrence of the 

 disease but with the original symptoms less pronounced. 



1 The annual death rate of employees of the French company (1882-1890) 

 was reported to be 231 per thousand. Under the later American control, 

 when the agency of mosquitoes in yellow fever and malaria had become 

 known, the death rate was reduced to 17 per thousand. There were no cases 

 of yellow fever from 1906 to 1911. 



