Zaria, Nigeria.—Nigeria is the most populous national state in Africa. It has a surface area of 356,669 square miles (about the size of the state of Texas). The southern one third of the country is composed largely of equatorial rain forest and contains six of the country's 12 states; the six remaining states cover the northern two thirds of the country, the area with which this article is concerned.
The annual rainfall of the coastal areas exceeds 100 inches. This diminishes northwards, the level at the northern border (the southern tip of the Sahara Desert) not exceeding 20 inches annually. According to the 1963 census, the total population was over 55 million. In 1973, the military government conducted a census, presumably a more accurate one, that gave a figure of 80 million. Population pressure is an important factor with respect to child health in the region. In the northern