Unless the world-wide birth rate is sufficiently cut within 50 years, "hungry and crowded people will rise in bestial strife," Dr. John Rock '15, Clinical Professor of Gynaecology, Emeritus, predicted on Wednesday.

In a speech at Mt. Sinai Hospital, New York City, Dr. Rock emphasized as axiomatic that the birth rate must be cut immediately. The great problem, Rock said, is to find an effective, humane, and universal means of contraception.

Dr. Rock mentioned a United Nations estimate that world population will rise 60 per cent in the next 25 years. Although advances in agricultural science will make an increase in food production possible, the population will rise even faster.

"In the Western Hemisphere, the U.S. is threatened by the high fertility rate in some countries south of the Rio Grande," said Rock. "Mexico and Puerto Rico are good examples," he added.

Rock feels that Communism or other radical movements may take control in underdeveloped lands, unless the population rise is kept under strict control.

The use of oral contraceptives, such as one tested in Puerto Rico for the past two years, is a promising development, said Rock. He called for increased research on all aspects of human fertility.