THE THYMUS AND MYASTHENIA GRAVIS

In a review of the relation of the thymus to myasthenia gravis in 1943, McEachern¹ suggested that the thymus functions to inhibit muscular contraction. The thymus is largest in fetal and postnatal life, when uninhibited violent muscular contractions might be harmful to the growing organism. Less adaptive inhibition would be involved as the child grows and is able to exercise more satisfactorily coordinated voluntary control of muscles. Hence the automatic mechanism responsible for muscular inhibition in postnatal life might be expected gradually to diminish.

If a large thymus persists, the accumulating effect of its muscle-inhibiting factor might be responsible for the symptoms of myasthenia gravis. McEachern was unable to demonstrate that extracts from the thymus could reduce the neuromuscular response to a given stimulus. Constant and his associates² at the University of Texas Medical Branch, Galveston, using a special technic devised by Porter and Wharton,³ recently demonstrated