stopped abruptly in 1902, and since that date there have been but a few sporadic cases. The record is as follows:

Gorgas was so impressed with the results that he soon sug

gested that similar measures should be taken for the Panama

germ.

district. In 1916 he made a preliminary survey for the Rockefeller Institution of the general situation in Central and South America and in 1918 a campaign was undertaken, calling for active measures under the coöperation of local governments. Meantime Noguchi had isolated the fever The success was immediate, as the accompanying chart indicates, and in 1925 only three cases were reported in the Americas. These were in northern Brazil. The fever broke out in Brazil in June, 1926, near the town of Parahyba where control measures had been stopped by the local authorities under the curious belief that they were spreading smallpox. General Gorgas died in 1920 while on his way to Africa to see what could be done there. The virtual elimination of yellow fever must be considered one of the greatest achievements of man, in part because it shows what can be done when man really understands nature.3

Malaria

Throughout all historic time malaria has been one of the greatest scourges of man, particularly in tropical and subtropical lands and in the moister portions of the temperate zones, decreasing in importance as the colder countries are reached, and is almost unknown in countries like Norway and Sweden. This disease is significant not only because of its share in the death rate but because of the long periods in which the patient is incapacitated for ordinary activity. It is estimated that there are from two to four thousand days of sickness for every death from malaria. When once it enters the system it may keep on recurring for months or years. The countries about the Mediterranean as well as the Caribbean and China have been hotbeds. On the island of Celebes, until 1922, it is said that "in the Dutch military encampment the brigades were often 'only able to march by combining two brigades into one."" During the late war an

observer of the troops in Macedonia wrote: "During one

period more men were invalided home than arrived on ships. I heard of battalions with 75 per cent of their men on their backs and of companies in which only five men were fit for duty." The experience of our men in Cuba in 1898 was similar.

Malaria is really a collective name, for there are at least three malarias now known to be caused by three animal parasites of the genus Plasmodium. The common malaria of the north, the tertian, is less serious than the æstivoautumnal of warmer regions and yields more readily to treatment. The discovery that malaria was due to a parasite (and not to the bad air emanating from marshes as the Italians had thought) was made by a French army doctor, Laveran. Long and tedious experiments by Ronald Ross in the malarial districts of India between 1895 and 1900 demonstrated that the disease was carried to man by mosquitoes of the Anopheles type. For this work Ross received the Nobel Prize in 1902. He was in charge of sanitation at Ismailia on the Suez Canal and by his measures was able to reduce the cases of malaria from 1,551 in 1902 to 37 (all relapsing cases) in 1905.1

The work of Gorgas at Havana and later at Panama was equally effective. He wrote that before 1901 "Havana had yearly from 300 to 500 deaths from malaria, rising as high in 1898 as 1,900 deaths. Since 1901 there has been a steady decrease in the malarial death rate . . . until 1912 when there were only four deaths. . . . By 1912 malaria had become as completely extinguished in Havana, as had yellow fever in 1902." 11

The efforts of the French to dig the Panama Canal were handicapped by disease more than by anything else and the chief diseases were yellow fever, malaria and dysentery. The newer evidence as to the two first diseases gave the Americans a great advantage. Gorgas sums up the situation by saying:

We had an average of 900 men sick every day. For the year this would give us 328,900 days of sickness, and for the ten years 3,285,000 days of sickness. If our rate had been 300 per thousand, a very moderate figure compared to what it was among the French, we should have had 11,700 sick every day. For the year this would have given us 4,270,500 days of sickness and for the ten years 42,705,000, a saving of 39,420,000 days of sickness during the period.

This is equal to a cash saving of $329,420,000.

During the ten years of construction, we lost by death seventeen out of every thousand of our employees each year. That is, from the whole force of 39,000 men, 663 died each year, and for the whole construction period we lost 6,630 men. If sanitary conditions had remained as they had been previous to 1904, and we had lost as did the French, two hundred of our employees out of each one thousand on the work, we should have lost 7,800 men each year, and 78,000 during the whole construction period.12

This means that 71,370 lives were saved.

Of the control of malaria, Osler has written:

From the very outset, malaria has been taken as the measure of sanitary efficiency. Throughout the French occupation it was the chief enemy to be considered, not only because of its fatality, but on account of the prolonged incapacity following infection. In 1906 out of every 1000 employees there were admitted to the hospital from malaria 821; in 1907, 424; in 1908, 282; in 1912, 110; in 1915, 51; in 1917, 14. The totalities from the disease have fallen from 233 in 1906 to 154 in 1907, to 73 in 1908 and to 7 in 1914. The death rate for malarial fever per 1000 population sank from 8.49 in 1906 to 0.11 in 1918.13

Here

The Rockefeller Foundation has also started a worldwide fight against malaria with promising results. again we have the possibility of destroying ultimately the Anopheles mosquito and thus getting rid of the disease which must lead a dual life, as it were, to survive. The

draining or filling of the swamps and other breeding places is difficult but not impossible. Meantime it is found that large areas can be poisoned by paris green and the distribution of this by airplane has been tried. If Americans would but resolve to extinguish the Anopheles instead of the wood duck the ultimate gain would justify the effort.

Hookworm.

The surveys of the International Health Board of the Rockefeller Foundation indicate that over half of the human race who live in a broad belt ranging about 35 degrees north of the equator to 30 degrees south, are heavily infected with a third animal parasite, the hookworm, of which there are several species. Over 90 per cent of the natives of Dutch Guiana, Colombia and Ceylon are affected, while in Alabama, Louisiana and South Carolina the percentage is about 50. The disease has been known for centuries but proof that it was caused by the worm was not furnished until about 1900. It belongs to the group commonly called "filth diseases" since the eggs are passed out of the body in the excreta to hatch and live in the ground for a time. Thence they get on the feet, particularly of those going barefoot, and make their way even through the unbroken skin. In the body the worm feeds on the blood to such an extent that growth is checked and the mental energies stunned, sterility may result, and the resistance to other diseases lowered. No disease of the tropics has more serious economic consequences. In as much as the worms live in the intestinal tract of man they may be reached directly by medicine and are readily destroyed by thymol. If the excreta are cared for further infection may be stopped. As soon as the history of the disease was known preventive measures were started with the happiest of results. The percentage of school children affected in Richmond County, Virginia, was reduced from 83 in 1910 to a little over 2 in