At noon on the same day, five minutes after the mosquitoes had been placed therein, a plucky Ohio boy, Moran by name, clad only in his night-shirt and fresh from a bath, entered the room containing the mosquitoes, where he lay down for a period of thirty minutes. Within two minutes of Moran's entrance he was being bitten about the face and hands by the insects, that had promptly settled down upon him. Seven, in all, bit him at this visit. At 4.30 p.m. the same day, he again entered and remained twenty minutes, during which time five others bit him. The following day, at 4.30 p.m., he again entered and remained fifteen minutes, during which time three insects bit him; making the number fifteen that had fed at these three visits. On Christmas morning, at 11 a.m., this brave lad was stricken with yellow fever, and had a sharp attack, which he bore without a murmur.
But still the demonstration was not complete. It was necessary to prove by equally undeniable evidence that yellow fever is not conveyed by contagion with the clothes and persons of infected people. These experiments were even more trying and heroic than those which preceded. A small wooden hut, 14 by 20 feet, was prepared, and into this was stored a large amount of bedding and clothes which had been used and worn by persons suffering from the fever. The building was carefully guarded against the intrusion of mosquitoes, and a temperature of seventy-six degrees, with a sufficient moisture, maintained. For twenty consecutive days Dr. Clarke and his men went into this room, handled, wore, and slept in the contaminated clothing, although the stench was so offensive as to be almost appalling. They emerged from the ordeal in perfect health, proving beyond possibility of dispute that the disease was not contagious, and that the mosquito was the sole method of transmission.
When distributing the credit for the new channel of world-traffic through the isthmus of Panama, let us not forget Dr. Lazear who sacrificed his life and the many others who cheerfully risked their lives to establish truths and facts without which the construction and continued operation of the canal would almost certainly have been impossible.
One mosquito may look very much like another, but the stegomyia and the anopheles differ in many important respects. The latter finds its most favourable breeding-places in stagnant pools of fresh water, such as are left by the heavy rains of the isthmus. It is essentially a gnat of the country-side. The stegomyia, on the other hand, inclines to a more frivolous town life. Cisterns and tanks and other receptacles for storing water are his favourite haunts. In length of life and power of flight the species also differ, though these details are not yet fully ascertained. The stegomyia is said to live three months. Dr. Cornish states that it becomes dangerous only by attacking man during the first three days of yellow fever, and that, even then, twelve days elapse before its bite is infectious. Six days after a man has been bitten by an infected stegomyia he falls ill with yellow fever, and for the next three days he is capable of transmitting it to the healthy mosquito. Mr. Bishop informs us that if there is no fresh case of yellow fever within a period of sixty days after the latest one in an epidemic, it is a safe conclusion that the disease has been stamped out, because there is no mosquito alive to carry the parasite. After a period of ninety days all doubt on the subject is removed.[9] If a community, therefore, which has thus got rid of its last case of yellow fever could be completely isolated, yellow fever could never possibly return. It could only be reintroduced from outside. It should be possible, with a proper system of sanitation and quarantine, to free any district entirely from this awful scourge.
The case of the anopheles and his little contribution to human suffering is very different. Whereas the victim of yellow fever either dies or gets better and quickly ceases to be a source of infection to the mosquito, the victim of malaria seldom dies of the disease, but he remains infectious to the anopheles for three years. The disease does not simply attack new-comers or white people. Natives of the isthmus and the West Indies are subject to it, and, indeed, seem to be in a chronically malarious condition. It is said that 50 per cent. of the population of the isthmus were found in 1904-5 to have the parasite of malaria in their systems. It is difficult to estimate or imagine the part played by this widespread malady on conditions of life and civilization within the tropics.
Sir Ronald Ross, the greatest living authority on the subject, made some interesting remarks in an address at the Royal Colonial Institute in January of this year. He said:—
Nothing has been more carefully studied of recent years than the existence of malaria amongst indigenous populations. It often affects every one of the children, probably kills a large proportion of the new-born infants, and renders the survivors ill for years; only a partial immunity in adult life relieves them of the incessant sickness. Here in Europe nearly all our children suffer from certain diseases—measles, scarlatina, and so on. But these maladies are short and slight compared with the enduring infection of malaria. When I was studying malaria in Greece in 1906, I was struck with the impossibility of conceiving that the people who are now intensely afflicted with malaria could be like the ancient Greeks who did so much for the world; and I therefore suggested the hypothesis that malaria could only have entered Greece at about the time of the great Persian wars. One can scarcely imagine that the physically fine race and the magnificent athletes figured in Greek sculpture could ever have spent a malarious and splenomegalous childhood. And, conversely, it is difficult to imagine that many of the malarious natives in the tropics will ever rise to any great height of civilization while that disease endures amongst them. I am aware that Africa has produced some magnificent races, such as those of the Zulus and Masai, but I have heard that the countries inhabited by them are not nearly so disease-ridden as many of the larger tracts. At all events, whatever may be the effect of a malarious childhood upon the physique of adult life, its effects on the mental development must certainly be very bad, while the disease always paralyzes the material prosperity of the country where it exists in an intense form.
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 with employees fleeing from this real "yellow peril." In the annual report of the Commission for 1905 we read:—
A feeling of alarm, almost amounting to panic, spread among the Americans on the isthmus. Many resigned their positions to return to the United States, while those who remained became possessed with a feeling of lethargy or fatalism, resulting from a conviction that no remedy existed for the peril. There was a disposition to partly ignore or openly condemn all preventive measures. The gravity of the crisis was apparent to all.