One striking experiment indicated that heredity can be a decisive influence. Ingalls said that when a completely different strain of mice--brown mice--were put in the vacuum chamber on the ninth day of pregnancy, more than 15 per cent of their offspring had hernias: yet there were no hernias in the offspring of several thousand white mice who had had the same experience.

"The probability is that constitutional susceptibility is inherited and that the specific defect is brought about by stress," he commented.

The studies on mice do not necessarily apply to humans, Ingalls emphasized; nor do the classic studies which showed how certain qualities are passed from generation to generation in flowers and insects.

Must Study Population

"The clinical case helps to point up the problem," he said. "Experimental genetics contributes to theory. Only through studying the population, however, can we hope to prove whether or not forces shaping sweet peas, fruitflies and white mice also govern the destinies of human beings."

At present, he admitted, it would be difficult to apply knowledge thus gained to improving the human race by improving mating habits.

"I have yet to see a young couple be introduced with the warning that the hand-some man is RH positive while the girl in the dress with the green sleeves is RH negative," he said.

But he felt that "outside the laboratory walls lies the real arena of life; the real challenge to use the forces determining health and disease to improve the quality of the newborn child rather than the quantity of our offspring."