The isthmus of Panama was beautifully adapted to the breeding of the _anopheles_ and the widest dissemination of malaria. In fact, the canal zone taken over by the Americans was perhaps the most malarial strip of territory in the world. The heavy rains leave the country covered with those marshes and pools from which these little ghostly insects are always rising in swarms, ready to carry the germs of disease from the sick to the healthy and thus perpetuate and extend the domain of this distressing malady. The reader will notice that, as the yellow fever victim is only infectious to the mosquito for three days, while the malarial person can convey the poison for three years, it is a much more practical problem to eradicate yellow fever than to stamp out malaria. It is true the causes of malaria are now fully known and the only effective methods of propagation ascertained. If one could isolate all malarial patients, including all who are capable of transmitting the disease, in buildings screened with fine copper-gauze to keep out the mosquitoes and thus gradually diminish the area of infection to vanishing point, it would not be necessary to deal with the breeding-places of the mosquitoes, and man and the gnat might live together in perfect amity. But with fifty and even seventy per cent. of the people malarially infected, such a heroic course is obviously impossible, and one can hope only to diminish to a considerable degree the prevalence of the disease. The first two and a half years of the American occupation of the isthmus was spent in looking round and preparing for the great work. It soon became evident that the most pressing and immediate task was one of cleaning up and sanitation. In July 1904, Colonel W. C. Gorgas, whose name will always be associated with the triumphs won over disease at the isthmus, became the head of the department of sanitation under the Canal Commission. He quickly recognized that everything depended on the efficiency and success of his own department. "The experience of our predecessors," he wrote, "was ample to convince us that unless we could protect our force against yellow fever and malaria we would be unable to accomplish the work."[10] When the Americans took over, yellow fever, though present, was quiescent, but the figures began almost at once to mount up. In December 1904 there were six cases on the isthmus and one death. In January 1905 there were nineteen cases and eight deaths, seven and one respectively among the canal employees. In May there were thirty-three cases, twenty-two on the canal, with seven deaths in all, including three employees. In June there was an alarming advance. Sixty-two cases occurred on the isthmus, thirty-four of them among the employees. There were nineteen deaths, six on the canal. Something like a panic then set in among the Americans engaged on the canal works. Many threw up their positions, and the homeward-bound steamers were filled