The delight which is experienced by those who discover new things in the various branches of science is, no doubt, very great. To reveal to other men processes, properties, existences in the natural world hitherto unsuspected, or, if suspected, yet eluding the grasp of man, is to do something which gives to him who does it a sense that he is of value in the world—a sense which will uphold him and enable him to endure adversity, and even persecution, with equanimity. But there is, perhaps, a greater and more vivid satisfaction for those who do or make great and splendid things which all men can see, and for which all men are grateful. The great artist—poet, painter, builder, or musician—has this satisfaction, and so also has the man who, by a combination of personal energy and clearness of intellectual vision, applies scientific knowledge to the accomplishment of great public works, and to the acquirement of that control by mankind of the natural conditions hostile to human progress which we may call, as did Lord Bacon, “the establishing of the kingdom of man.”

The men who have expelled yellow fever from Cuba and Panama have not merely done a piece of sanitary cleaning up; they have first imagined and then created, by the force of human will, directed and maintained by conviction of the reality of science, a new thing—the tropics without deadly fever, the tropics as a healthy and welcome home for the white man. That is comparable to the work of a great artist in the directness of its appeal; it is in its actual detail the result of the combination of the skill of the engineer with the foresight and absolute domination of his human agents of a military genius.

For this magnificent work the highest credit is due to the United States chief sanitary officer, Colonel Gorgas. It is well known how the American Medical Commission in Cuba proved six years ago that yellow fever is conveyed from man to man solely and entirely by a gnat common in Central America, known as Stegomyia, and further, how by carrying out measures for preventing the entrance of these gnats into dwelling-houses, and especially by keeping them away from yellow fever patients so that they fail to obtain and carry the yellow fever germ, even if they do bite healthy men, Colonel Gorgas and his associates practically eradicated yellow fever in Cuba. The bite of the Stegomyia gnat is the only way in which a man can acquire yellow fever, and the gnat which bites him must have taken up the germs of yellow fever from another man—twelve days (no less) previously.

The application of this knowledge and the methods devised to give it effect is what has now rendered the construction of the Panama Canal by the United States Government possible. The French Canal Company employed an army of labourers, numbering from 15,000 to 18,000 men. They lost, almost entirely by death from yellow fever and malaria, so many of their workmen that others refused to undertake the deadly job, and there was a general panic. The death-rate was in 1884 over 60 per 1000. In 1885 it was over 70 per 1000. The work was abandoned. In May 1904 Colonel Gorgas and his forces took possession of the canal zone. This is a zone of territory running fifty miles north and south, with a good-sized town—Colon—at one end of it and another—Panama—at the other end of it. Many hundreds of men were at once organised and set to work to destroy in both the towns the Stegomyia gnat. This was effected by doing away with all the breeding-places of the gnat, that is, screening and covering every water receptacle in the town, so that the gnats or mosquitoes cannot breed. Then a fumigating process was carried out in all houses and buildings, great and small, to destroy such gnats as were still alive. No less than 200,000 lb. of pyrethrum and 400,000 lb. of sulphur were used in this fumigation. In December 1905 the last case of yellow fever occurred. It took sixteen months of the work just described to effect this.

In a different way the Anopheles gnat or mosquito, which carries the germ of malaria from man to man, was got rid of. This gnat breeds in clean water, where grass and weeds grow; it belongs chiefly to country districts. As it rarely flies more than 200 yards it was sufficient to destroy the breeding pools within that distance of the workmen’s houses, camps, and villages. All the windows and doors of all houses were fitted with wire-gauze screens, which prevent the entrance of the gnats, and the population was furnished with quinin, a dose of 3 grs. a day being ordered to bring the men into such condition that the malaria parasite would not thrive in the blood even if introduced.

The object with which Colonel Gorgas and his associates started was accomplished in less than two years. The control of yellow fever and malaria has become even more complete in the two years which have followed. It is two years since yellow fever disappeared from the entire zone, including the two towns. Malaria has not been so completely destroyed. The employÉs of the Canal Commission and Panama Railway now number 45,000. The death-rate of this entire force, including both black (33,000) and white (12,000) employÉs, was, in the month of December 1907 only 18 per 1000 per annum—less than that of the city of Liverpool, which was 20, or that of Salford, which was over 19. Of all the white employÉs the death-rate was only 13 per 1000 per annum. In the year 1906 (whole year), among the 6000 white employÉs who had come from the United States, including some 1200 women and children, their families, the death-rate from disease was only 4 per 1000. Pneumonia has been a chief cause of death among the negro labourers, but seldom affects the whites. Malaria caused, in the whole army of labourers, only six deaths in December 1907, as against thirteen in the smaller army at work in the same month in 1906. There were 800 cases of malaria in the whole army of 45,000 employÉs in December 1907.

It is thus apparent that Colonel Gorgas has converted this deadly zone from which negroes and white men hurried in a panic of fear twenty years ago into a region as healthy—that is to say, with as low a death-rate—as an ordinary North American or English city. No doubt allowance must be made in the comparison for the special nature of the population brought together on the canal zone. This is favourable to a low death-rate, in so far as it consists of strong adults, excluding old people and very young children, but unfavourable in so far as it consists of negroes and mean whites, who are even less amenable to sanitary regulations and precautions than the population of an English city. Colonel Gorgas writes that now that it is shown that any population coming into the tropics can protect itself against yellow fever and malaria by measures which are both simple and inexpensive, the Anglo-Saxon will find life in the tropics more healthful than in the temperate zones, and tropical countries which offer a much greater return for man’s labour than do those of the chilly temperate zone, will be in the course of the next two or three centuries occupied and populated by the white races. Such an unpleasantly cold spring as that which all Europe endured last year makes one wish that the tropics generally were already arranged by Colonel Gorgas for our reception, and provided with a sanitated white-faced population. We could go and live there, warm and comfortable, all the year round, enjoying the rich luxuriance of tropical nature without fear of either chill or fever.