Abstract
Animals were stimulated with a tone of about 13,400 c.p.s. (compressed-air activated Galton whistle) beginning at about 30 days of age and at 30- to 50-day intervals until about 300 days. Over half of all "susceptible" animals exhibited first symptoms of susceptibility by 90 days, but some animals exhibited these symptoms for the first time at ages of > 240 days.