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present. The cause of cancer is unknown, but it is generally believed to be a germ of some sort. The recent hopes based on the announcement from some of the best men in America and France that cancer is yielding to radium treatment are now being surrendered. Whether this proves true or not it is believed that sooner or later its secret will be revealed. It is claimed that each year in Germany more women die of cancer than there were men killed in the whole Franco-Prussian War. The chart on page 141 shows that we are controlling tuberculosis while cancer is steadily increasing. The figures are from New York.

A world-wide war has been declared on disease. The dreaded sleeping sickness which has depopulated Uganda, the anemia which makes wrecks of the natives of Porto Rico and the tropics, the hookworm disease which came to America with the slaves from Africa are better understood and are being conquered. The movement inaugurated by the chemist Pasteur has revolutionized the function of medicine and the doctor with his "pill for every ill" yields place to the research student who strikes at the source of disease.

This new warfare uses several methods as has been indicated. In a few cases long experiment reveals some agent or compound like salvarsan (arsenic) discovered by Ehrlich and first known as No. 606 (that number representing its order in his experiments), which in most cases kills the germ of syphilis. In the second case we use modified forms of the disease or its own deadly by-products to bring about its prevention or destruction, and finally we endeavor to prevent infection by destroying the germs just as we have destroyed the great auk.

Beside the doctor to whom we go voluntarily in sickness has arisen the medical officer of the state backed by law to safeguard public health. State commissioners of health or boards of health supervise matters within the state. Since 1893 all maritime and interstate quarantine powers of the national government are controlled by the Public Health Service under a supervising surgeon general. This service establishes quarantine regulations for all ports of the United States and has gradually taken over control of the ports, maintaining now some fifty stations in addition to those on the Islands and in Alaska. So recent has this development been that the ports of Boston, Baltimore and New York are still under local control. So little anticipated were these functions that even today if a serious epidemic breaks out in some state the national authorities can only interfere if there is danger that interstate commerce in goods will be affected.

Meantime great research laboratories have grown up in connection with city or state departments, in medical schools, or special institutions like the Rockefeller Institute for Medical Research in New York City, or the Pasteur Institute at Paris. Chairs of tropical medicine are found in our schools and special public health courses appear in the curricula. The doctor has joined forces with the social worker and the demand is that preventable disease shall be no more. In no period of earth's history has so much been accomplished as in the last fifty years. Small wonder that man is encouraged to hope that a real and effective control of these natural enemies will soon be in his hands.

In many ways quite as important as the control of diseases affecting man is that of those destroying his plants and animals, for they too are subject to attack. Tuberculosis has already been mentioned in this connection, and from one-third to one-half of our cattle are said to be infected. Borna's disease, a form of meningitis, destroyed some 20,000 horses in a few weeks in 1912 in Kansas and adjoining states. The cattle plague (Rinderpest) has repeatedly destroyed the herds of the Herero Negroes and it is stated that probably not one in ten thousand wild buffalo in west Africa and Uganda survived the last epidemic some twenty-five years ago.

The financial loss entailed by disease among domestic stock is enormous as our government reports reveal.

Live Stock - Losses from Disease in United States

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Considering three of our common food animals we find

a reported loss in 1913 in the United States:

Swine, 119 out of every 1000 or 7,005,000 from cholera chiefly

Cattle, 19 out of every 1000 from diseases

Cattle, 10 out of every 1000 from exposure

Sheep, 42 out of every 1000 or 1,737,000 from disease and exposure

Total money loss

..$150,000,000

Some 200 insects attack domestic animals in this country. If we are to protect ourselves from great loss as well as from disease, we must control the fleas, flies, ticks, and other germ-carrying forms. By a direct warfare on ticks we have checked the spread of such diseases as "Texas-fever" among the stock; and the Bureau of Ani

mal Industry was able to report in 1914 that 30 per cent of the territory formerly cursed by ticks was free from them and the quarantine lifted. Ten per cent of the calves in some regions were formerly lost through blackleg. Now by the use of a virus the loss is less than .5 per cent. Sheep scab and cattle mange are now eliminated on 135,000 square miles formerly quarantined. We have recently discovered that tapeworm cysts are rather common in sheep and we shall have to guard against a possible infection of human beings. About 160 persons die of rabies and the Pasteur Institute treats some 1500 patients each year. If we are to rid ourselves of this dread disease we must stamp it out in the animals. The epidemic of "foot and mouth" disease of 1914 and 1915 did enormous damage, compelled the destruction of valuable herds of stock and interfered with commerce and ordinary farm life in many ways. It was overcome by government action, otherwise we might have lost most of our cattle.

To these problems man has given great attention and veterinary science has rapidly advanced. The story of the man who applied to the government for advice as to treatment of the sick pig and was told how to cure it, while his neighbor was informed that the government could give no aid to his sick wife, really illustrates the relative attention given by our national government to the welfare of plants and stock. Disease-resisting plants have been found or developed. The farmer may get numberless pamphlets and volumes free by request from state or national agricultural departments. The transportation of plants and animals even between the different states is carefully regulated lest disease be carried. In the fall of 1913 the importation of potatoes from certain foreign territory was suspended because of disease there, and similar prohibitions frequently prevail. In 1916 the spread of the white pine blister rust began to threaten our pine forests and the importation of nursery stock from Europe was prohibited. These measures may not be adequately carried out in all cases, but they show that man has come to see the nature of his task in this regard and is determined to devise satisfactory methods of protecting himself and his. Let no one get the impression that man wholly controls the situation. The blight that is destroying our native chestnuts presents a problem which no man can yet solve. In Ceylon the coffee industry was entirely destroyed between 1870 and 1890 by a fungus which fed on the leaves of the bush.

We have now hurriedly surveyed three of the chief fields in which man's control of nature may be seen: (1) physical materials, (2) food plants and domestic animals, (3) diseases. By his control of materials and natural forces he drives his engines and constructs his machines and buildings. In limited areas he modifies temperature and protects himself against the weather. From plants and animals he gets his food and clothing. Hence he has spread over most of the earth and made himself at home. Of the higher forms of life he alone and those of the lower that he protects are increasing steadily. It is common to speak of his marvelous progress in control. It seems to me more correct to say that he has made some promising beginnings. Over wind and wave he exercises little mastery. The wonderful energy of the tides and the rays of the sun still await his call. The mass of element he rarely uses and the bulk of the forms of life are of little service, to say nothing of his controlling them for his purposes. Disease weakens his strength and that of his animals. Weeds hinder his agriculture. The point

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