INSECTS AND HUMAN DISEASE 91 



the French work in this district, the discovery of the 

 relations existing between these dread diseases and mos- 

 quitoes had been made known, and were certainly not 

 generally available. The American efforts were at first 

 directed against the yellow fever mosquito, and, when it 

 had been practically eradicated, attention was turned to 

 the malaria mosquito, with equally successful results. 

 But a permanently mosquito-free territory, through arti- 

 ficial means, is impossible in such a climate as that of 

 Panama. "The battle with nature is unending, and the 

 slightest relaxation means reversion. . . . Special and 

 exceptional problems are being constantly presented, due 

 in many instances to the engineering work connected 

 with canal construction. Swamps of large area are some- 

 times unavoidably created, and before drainage can be 

 effected, breeding of Anopheles has assumed formidable 

 proportions. . . . The great Gatun lake, with its approxi- 

 mately two hundred square miles of area and hundreds 

 of miles of rugged shore line, bids fair to offer many 

 problems as its level continues to rise. In the sheltered 

 bays and indentations of its shore line, aquatic vegetation 

 riots, and, as the waters inundate the tropical forest, a 

 condition is created, ideal for the most prolific breeding of 

 Anopheles and other mosquitoes: a tangle of living and 

 dead vegetation, with floating debris from the dying trees, 

 among which water plants flourish. A large part of the 

 breeding areas formed will probably affect only scattered 

 habitations and ranches, but, wherever settlements and 

 towns are contiguous to the permanent shore line, correc- 

 tion of these conditions will be imperative. It is obviously 

 impracticable to thoroughly clear and control square miles 

 of territory, covered with heavy timber, and soon to be 

 buried beneath the waters of the lake, but until the per- 

 manent level is reached the uncleared and shallow margins 

 of the lake will supply myriads of mosquitoes to the 

 adjacent regions." 



