Fifty-four thymus glands removed surgically from patients with myasthenia gravis were examined using an accurate morphometric technique and the data compared with the response to thymectomy. There is a tendency for patients with relatively unreactive thymus glands to obtain a better result from thymectomy but this is not statistically significant.

A characteristic of the normal thymus gland is its rapid growth during the early stages of life followed by a progressive involution as the animal ages. On the other hand, in the Akr strain of mice a marked hyperplasia of this gland usually occurs in those animals which develop lymphatic leukemia. In this strain the thymus is believed to be the primary site of leukemogenesis (6). In the followi...