Bednar (1852), Vogel (1856), von Mayr (1862) described briefly the percussion signs of the enlarged thymus. Sahli1 (1882) first made an extensive study of these signs on living subjects. Blumenreich2 (1902) investigated the signs on dead subjects, comparing the shape of the percussion dulness with the exposed portion of the gland as revealed at the subsequent autopsies. The principles for determining the thymus by percussion, as laid down by Sahli and modified and amplified by Blumenreich, hold to-day. They have the confirmation of anatomical fact. There have been advanced, however, two percussion methods for the recognition of the enlarged thymus which rest on anatomical hypotheses. The present paper is a discussion of the anatomical conditions underlying these two methods.
While the methods of Sahli and Blumenreich are directed at the more exact determination of the outline of percussion dulness, the methods in question — those of Jacobi3 and