vin CONQUEST OF DISEASE 203 



means of converting the same places into tropical health 

 resorts. 



When nothing is known of the natural laws of a disease 

 mankind is helpless against it ; but when science has 

 discovered the enemy a sound basis can be secured for 

 a plan of campaign to exterminate it. Plague has- to 

 be fought by the destruction of rats where it prevails, 

 as well as by better housing and sanitation ; malaria 

 and yellow fever have to be kept under control by the 

 continual clearance of breeding- places of mosquitoes in 

 infected areas. Administrative measures based upon the 

 teaching of science have practically abolished plague 

 from the cities of Europe, have cleared Havana, the 

 Isthmus of Panama, the West Indies, and Rio de Janeiro 

 of yellow fever, and have made the Roman Campagna 

 almost free from malaria, though formerly few men 

 who went to the district could hope for more than three 

 years of life in it. 



Practical acquaintance with ailments may be obtained 

 by watching the sick and administering drugs, but this 

 clinical experience is not of much use in determining the 

 nature and origin of disease. For centuries, physicians 

 have made their comforting presence felt at the bedside 

 of their patients, but their observations have contributed 

 little to the -knowledge of the causes of diseases, the 

 means of conferring immunity, or of providing anti- 

 toxins or chemical antidotes which by their specific 

 action upon the virus of diseases successfully save human 

 beings, as well as the lower animals, from death and 

 incapacitating illness. 



In the struggle against diseases and the discovery of 

 means of stamping them out and preventing their 

 development, we must not look for help to the popular 

 physician, but to the bacteriological or the chemical 



