and hospitals came into favor. Unfortunately the gathering together of the sick and injured favored the spread of various bacteria whose presence was hardly suspected, with the result that hospital operations were accompanied by a high mortality rate. This attracted the attention of many physicians, among them Lister, who sought some solution. In 1865 he began the use of carbolic acid and obtained such excellent results that he called the attention of the profession to his success. The necessity of a change is shown by the results of an investigation made in 1869. Out of 2,098 amputations in country practice, 226 had proved fatal, but 2,089 hospital amputations showed 855 fatalities. The investigator, Sir James Simpson, said: "Most hospital surgeons ever remain content with losing one-third to one-half of all their amputation cases, and nine-tenths of some." 17 The French hospitals during the Crimean War had a frightful record. "Out of 13,173 amputations of all kinds, including those of fingers and toes, 10,006 proved fatal." 18 Lister early learned of Pasteur's studies on fermentation and putrefaction and became an enthusiastic supporter. Lister's fame spread rapidly. The German surgeons sent to him for aid. A new era dawned and the contrast is best shown by a little table: The mortality of ovariotomy, formerly 60 per cent, is now 2-3. The mortality of compound fractures, formerly 60 per cent, is now 3. The mortality of major amputations, formerly 50-63 per cent, is now 10-20. In 1870 all openings of head, chest, and abdonien were considered almost necessarily fatal and were only made when death was otherwise certain. Now they are practically without danger. The old death rate in hospitals of women at time of childbirth was alarming. From 1803 to 1833 the Pennsylvania Hospital had a record of 5.6 per cent. In an epidemic at the Bellevue Hospital in 1872 the death rate rose to 18 per cent. When it was discovered that this was due to bacterial infection improvement was possible. By 1909 the New York Lying-In Hospital reported that only 0.34 per cent of 60,000 obstetrical cases were lost, or one out of 1,250. In good hospitals to-day the loss does not exceed 0.25 per cent.19 Knowledge of the minute forms of life and the means for their control has made man master of the situation. Space limits prohibit detailed consideration of other diseases and the treatment now given them. This chapter makes no pretense of giving a summary of disease. The illustrations have been chosen to show man's relations to other forms of life and the advance made possible by understanding these relations. Incidentally they show most of the methods employed in fighting the disease, and some of the dangers involved in migration and commerce. Man must eat the lower organisms in order to live. He must also prevent them from eating him, and this is much more difficult. Formerly man feared the bigger animals, now he must devote his attention to minute enemies. It requires brains to fight invisible enemies. Can the man in the street be educated to the point where he will follow trained leaders? The problem of health has become social rather than medical. We must turn from the doctor with "his pill for every ill" to the sanitary engineer and must be willing to pay the doctor for keeping us well rather than for curing us after we are sick. It will have been noted that few specific remedies have been found for diseases. Quinine will kill the germs of most malarias but it is better to kill the mosquitoes. Iron attacks anemia. Mercury and arsenic are fatal to the germs of syphilis. Chaulmoogra oil appears to be working wonders for the victims of leprosy in the colony at Culion. We may hope for the discovery of other specifics but in most cases we must turn the enemy against itself as in typhoid, smallpox, diphtheria, and tetanus. THE DEATH RATE The results of all this newer knowledge are shown by the steady fall of the death rate in civilized lands. In 1875 the death rate in New York City was 28.3 per thousand; in 1925, it was 11.5, a reduction of 59.4 per cent. In 1868 the death rate for children under five was 124.8 and in 1920 it was only 30.8. By contrast the death rate in 1868 for the age periods forty-five to fifty-four was 22.1 and in 1920 it was 32. For a good many years the Metropolitan Life Insurance Company has conducted a campaign of health education among its policyholders. The results since 1811 are almost astounding. The reduction between 1911 and 1925 was 56 per cent for tuberculosis, 80 per cent for typhoid fever, from communicable diseases of childhood 55.5, from diphtheria 62. The downward trend of the death rate in the registration area of the United States is shown in the following diagram, which reveals a drop from 10.1 in 1911 to about 8.6 in 1926. The sharp rise in 1918 and 1919 was due to the epidemic of influenza. Striking as these figures are it will be noticed that the chief reduction is in the case of children. As we raise the average age of the population we must expect an increase of deaths in the later years. This may be in part the explanation of the increase of cancer, which is rapidly rising to the top of the list, a disease, moreover, whose cause is unknown. Degenerative diseases are becoming more common also. "The real risk of dying from cancer increased from 4 to nearly 60 per cent at various ages for males and from about 18 to nearly 70 per cent for females between 1910 and 1921. The heavier increases at the later ages affect, however, only a small number of lives exposed in a life table population." 20 It is claimed that over 30,000 per 1000 10 Death Rate 15 young men and women between the ages of twenty-five and twenty-eight die each year from preventable causes in the United States. 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 FIG. 7. DEATH RATE FROM ALL CAUSES IN THE UNITED STATES REGISTRATION AREA Increase in Life Span Possibly a better way of estimating the advance we have made is the increasing length of life. In 1880 the average life of a citizen of New York was about forty years, now it is fifty-five or fifty-six. In 1901 a baby born in the United States might expect a life of 49.24 years, now the expectation is 57.32. It is claimed that the average length of life in Europe in the sixteenth century was eighteen to twenty years, whereas as many people now live to be seventy in Geneva as lived to be forty at the earlier period. Sweden shows an addition to average life of fourteen and onequarter years in the last ten decades. When accurate statistics were first kept in England only 31 per cent reached the age of sixty-five, now some 47 per cent are said to attain that age. In India, by contrast the average age at death is said to be twenty-three for men, and twenty-four for women, with little change in recent decades. This saving of life means also a decrease in number of sicknesses and a consequent improvement in regularity of work and in productiveness. While man has not solved his problem of disease he has greatly improved the conditions of life and may expect even better things in the future, Provided. PLANT AND ANIMAL DISEASES The increasing dependence of man upon domestic animals and cultivated plants makes the problems presented by their diseases hardly less important than his own health. There are two reasons for this. First, disease may reduce the amount of his products or injure their quality, and, second, the animals may be intermediate or alternate hosts of diseases to which man is liable. In as much as the treatment of these diseases introduces no new principles, no extended discussion is necessary. About the only differences observable are that the animal cannot lie to the doctor and that man is more interested in preventing the spread of plant and animal disease than in curing the sick individual. Diseases of Plants All cultivated plants are attacked by various fungi, some native, some imported. The cost to man runs into enormous figures. Only by exercising the greatest care can the greenhouse manager prevent plant disease. Sometimes the fungus attacks one type of plant, sometimes it spends part of its life cycle on one host and thence makes its way to another. The white-pine blister rust which threatens our native pines was widely established in the East by 1916 and had been carried from France to British Columbia by 1910, thence spreading on the north Pacific coast. This fungus requires some intermediate host like the gooseberry, black currant, barberry. Only by eliminating these shrubs can we save the pines. The rust infection of spring wheat in |