TRANSMISSION OF DISEASES BY INSECTS 257 



similar population 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. 



After serving as Surgeon General of the United States Army from 

 1914 to 1918, W. C. Gorgas entered the service of the International 

 Health Board, and was organizing an international campaign against 

 yellow fever at the time of his death in London, July 4, 1920. 



General Gorgas attained international preeminence for his ability 

 in organizing and conducting operations of magnitude against insect- 

 borne diseases. On account of his services in the protection of human 

 life his assistance was sought by foreign nations, and he received high 

 honors. 



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 some- 

 times 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 domestica, which is by far the commonest fly found generally 

 in houses, and becomes a serious menace to health during epidemics of 

 typhoid fever. 



The house fly is well adapted by its structure and habits to carry 

 bacteria. The adults often feed on substances contaminated with 

 typhoid or other bacteria and these infected substances cling readily 

 to the hairs of the insect, especially those of the feet, and to the pro- 

 boscis. The larvae develop chiefly in horse manure, but also in other 

 kinds of excreta, some of which may contain virulent typhoid 

 bacilli. 



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