Four months ago when I decided on the title of this talk, perhaps I let my vanity lead me astray, for it tempted me with a resounding title. How easy it is to shout loudly from a distance, like a passing motorist whom you have displeased and who courageously gives you a piece of his mind! He knows he is safe from you because he will be half a mile away in 30 seconds. When I was 3 months and 10,000 miles away and did not have this talk prepared, I must have been somewhat like that motorist. But, unlike him, I cannot get away and my enemy, time, has caught up with me, and I have now to justify the loud shouts which I issued from down under. In New York a few days ago I was discussing this title with Dr. Peyton Rous of the Rockefeller Institute, and