 It was observed, however, that when pre-adolescent animals are thymectomized, they experience a variety of maladies including increased incidence of infection, failure to grow, neuromuscular disorders, cancer, etc., collectively known as “wasting disease”.The greater susceptibility to infection was shown to be directly attributable to a dramatic decrease in peripheral blood lymphocytes in thymectomized animals.By 1964 it had been demonstrated that regulatory factors extracted from the thymus gland could prevent many of the manifestations of wasting disease.