and of natural disease. Practically, however, this would be of little difference; the leather made from the hides of animals dead of old age would be of so low value as to be almost worthless; and the use of the hides of animals dead of disease, many forms of which are infectious and communicable to man, would be fraught with danger and difficult of execution. Mankind would have to face the problem of clothing without the aid of leather and fur.
Can the surface of the earth (for the fishes of the sea would have to be excluded) raise enough grain, fruits, nuts and vegetables, added to dairy products, to meet the albumin needs of the present earth's population? Unhesitatingly it may be stated that the area of the earth's surface now under cultivation could not, with the present methods of agriculture, dependably produce enough plant albumin to meet the needs of the present population. Very large areas of the earth's surface at present produce only grasses, shrubs and trees. Man can neither graze nor browse. At present these plants are consumed by cattle, goats, sheep and swine, whose albumin is utilized in turn by man. It is through the mediation of these animals that the vegetation of enormous areas of land is made available for mankind. At present probably one half of the albumin needs of mankind are met by animal albumin. To meet these needs with plant albumin and dairy products the world's production of grains and legumins would need to be doubled at the least. It is quite certain that this could not, with the uttermost efforts of the world's population, be dependably accomplished at present. It is possible that it might be accomplished, with the present methods on the present acreage of tillable soil, if no untoward manifestations of the elements occurred (such as severe winters, unseasonable frosts, floods, droughts, storms, excessive heat), with a dependable rain-fall in both time and space. But mankind would be yearly at the mercy of the elements. To meet fully and safely the needs of the growing population, four scientific advances of monumental magnitude would need to be attained.
The methods of the cultivation of the soil must be so intensified and revolutionized through scientific investigations as to make the yield of the soil less disproportional to its potential.
The conservation of water must be accomplished on a scale never before dreamed of.
The world-wide ravages of the parasitic diseases of plants must be checked.
The conversion of inert atmospheric nitrogen into potential soil nitrogen must be accomplished upon a vast scale through microbic and electro-chemical agencies.
The results of the accomplishment of these four advances, judged merely from present scientific knowledge of the possibilities in the four