Population growth rates in perfect contraceptive populations.

Abstract Eventually, world population must cease to grow. In many countries attempts are made to decrease population growth by providing family planning services to all who want to prevent pregnancies. In this paper we use the concept 'perfect contraceptive population',(1) - a population in which no unwanted births occur - to derive estimates of the maximum contribution that prevention of unwanted births might make toward attaining a zero rate of natural increase in population.

The oceans: growth and oxygen isotope evolution.

A study of the evolution of the oxygen-18/oxygen-16 ratio of the oceans suggests that this ratio is unlikely to have remained constant with time. Our models suiggest that early formation of the oceans is more likely than linear growth.

INTESTINAL OBSTRUCTION : II. A STUDY OF THE FACTORS INVOLVED IN THE PRODUCTION AND ABSORPTION OF TOXIC MATERIAIS FROM THE INTESTINE.

1. It is impossible to sterilize the intestine by the use of chemical antiseptics even when these are applied directly to the mucosa of isolated segments. 2.