Though first described by Cruveilhier1 in 1829, cysts in the thymus of the new-born were first carefully studied by Dubois2 twenty-one years later. By this author they were considered abscesses, on account of their purulent contents, and as all of his cases were in infants who showed definite evidences of congenital syphilis, he regarded the condition as of syphilitic origin.
In the following years of gross pathology numerous cases of "abscesses" of the thymus were described, but it was not until the microscopic study of Chiari3 that the true nature of these structures became known. In a male infant which died a few minutes after birth and which showed pronounced syphilitic lesions (pneumonia alba, hepatitis, pancreatitis, and osteochondritis syphilitica), he found the thymus, which was not enlarged, to be filled with cavities which contained purulent material. Microscopically, however, these cavities proved to be not abscesses, but cystic