242 ENTOMOLOGY 



to the presence of the disease. The city was freed from the fever before 

 frost came, by the same methods that had proved successful in Cuba; 

 but not without organized work of the most strenuous kind on the part 

 of the citizens, under the direction of the U. S. Public Health and Marine- 

 Hospital Service. At present the yellow fever mosquito is said to be a 

 rarity in Louisiana owing to the vigorous measures enforced in its sup- 

 pression throughout the state. 



Fever in the Canal Zone. The Panama Canal zone was formerly 

 one of the most unhealthful places on earth, chiefly on account of the 

 prevalence of malaria and yellow fever. When the United States ac- 

 quired the zone in 1904 it was realized that the first step toward building 

 the great canal was to protect the health of all those immediately con- 

 cerned in the undertaking, and the sanitation of the isthmus was placed 

 in charge of one eminently qualified for the work, Colonel W. C. Gorgas. 



He adapted the methods he had used in Cuba to the conditions 

 existing on the isthmus, with the result that every year the death rate 

 decreased until in 1908 it became, among eight thousand white Americans 

 living there, 9.72 per thousand, "a rate no higher than for a similar popu- 

 lation in the healthiest localities in the United States, and much lower 

 than that for most parts of the country." The Sanitary Department 

 has succeeded in driving yellow fever from the isthmus and in checking 

 malaria and other diseases to such a degree that the canal zone is no 

 longer an unhealthful place. 



TYPHOID FEVER 



The specific cause of typhoid fever is Bacillus typhosus. In the 

 human body this bacillus occurs chiefly in the intestines; but also in the 

 urinary bladder and usually in the blood of infected persons. 



The excreta of typhoid subjects contain the virulent bacilli; and some 

 persons, even after recovery, continue to be "chronic carriers" of the 

 disease for many years. 



Transmission. The typhoid bacillus is introduced into the human 

 system by eating or drinking. Most epidemics are due to infected 

 water and many to milk; occasionally the disease is acquired from raw 

 vegetables or from oysters contaminated with sewage. Often the bacillus 

 is conveyed to food by human hands and possibly it is sometimes carried 

 by dust, cockroaches or ants; but there is no doubt that the disease is 

 transmitted by certain flies, particularly the true house fly, Musca domes- 

 tica, which is by far the commonest fly found generally in houses, and 

 becomes a serious menace to health during epidemics of typhoid fever. 



