The Span of Life Lengthened by Medical must not be supposed however that the increase of transporting power has been the only cause of the marvelous increase in popula tion which has characterized the past century. Medical science and hygiene have greatly de creased infant mortality and increased the span of life for those reaching maturity. No exact figures can be given by which to compare these conditions of the present time with those of a century ago, but it is an accepted fact that the "expectation of lifex' for the average human being is now much greater than formerly. And this has been a factor of considerable im portance in the growth of world population.
Use of Machinery in Food Production.— Another factor is the ease with which food may now be produced through the use of machinery, which has thus reduced the amount of human labor and time required to produce a given quantity of the requirements of man. The United States Department of Agriculture states that the amount of human labor now required to produce one bushel of wheat is but 10 minutes against 133 minutes in 1830. This marvelous change is the result of the applica tion of machinery to the preparation of the land, the planting of the seeds and the harvest ing and threshing of crops, while the labor re quired to turn it into form for food has also been greatly decreased. The great slaughtering houses which now turn cattle and swine into fit form for food receive an endless procession of living animals at one entrance and with a few minutes of labor turn out the finished product at the exit, sending the fresh meats by refrig erator cars and vessels to the markets on the opposite side of the globe and at the same time so conserving the by-products that the waste which accompanied the crude methods of former years no longer exists.
New Foods Increase the Power to Sustain reason for the increase in power of the world to supply the require ments of man is found in the acceptance of new varieties of food which the increased facilities of transportation can now bring from other parts of the world or introduce for adaptation to the soils of countries in which they did not formerly exist. We of the United States, for example, are now bringing into this country over $100,000,000 worth per annum of food oils or the material from which they may be produced as against $15,000,000 a decade ago, and this use by us of the untold quantities of a highly valuable food formerly going to waste in all parts of the tropics is also occurring in other parts of the world, especially the densely populated countries of Europe, which are rapidly increasing the use of vegetable fats from the tropics. Sugar, an extremely valuable article of food, has developed with astonishing rapidity as a result of cheap transportation and better process of manufacturing, and the world's pro duction of sugar in the year preceding the war was 40,000,000,000 pounds against 4,000,000,000 pounds a half century earlier. The world's
corn crop of which the United States is the world's largest producer is now about five times as much as 50 years ago. Meantime we have brought from other parts of the world many grain and other food products and so adapted them to our own soils and climate as to materially increase our power of sustaining a large population.
Increased Density of Population no Longer Considered Alarming.— Even those sections of the world long looked upon as densely populated go calmly on increasing their populations at a rapid rate and producing the bulk of their own food by the exertions of their own people. Japan, for example, one of the most densely populated countries of the Orient, has doubled its population in less than 50 years, yet it imports comparatively very little food stuffs, drawing its chief food supply from its rice fields with which the mountain sides are terraced and the surrounding seas whose fish eries supply practically all of the animal food consumed by the people of Japan. These require the time of about 2,000,000 people in accumulat ing and preparing the nearly $100,000,000 of sea food which that industrious people draw from the surrounding waters. Java., the most densely populated island of the world, has doubled its population in less than a half century, and its people, who now average more than 700 per square mile for the entire island, draw most of their food from the rice fields and the fishing industry, and have rendered the island ex tremely prosperous with such valuable products as coffee, tea, sugar, spices, cinchona, tin, petro leum and India rubber, which they exchange with other parts of the world for such require ments as they are not able to meet from their own sources of production. Germany, with an area less than our State of Texas, had doubled its population between 1840 and 1914, and with a population 10 times as dense as our own was, be fore it entered upon the great war, looked upon as one of the most prosperous countries of the world, drawing much of its food and manufac turing material from other sections of the globe and paying therefor with the product of the manufacturing industries. England, with a population much more dense than that of Ger many and equally dependent upon other coun tries for food and manufacturing material, doubled her population in the past 60 years and ranks among the most prosperous of the world's nations, bringing its food and manufacturing materials from long distances and paying for them with the products of her work shops.