Anomalies of the thymus gland are even rarer than those of the thyroid body; the only abnormal conditions with which we are at present acquainted are a more or less considerable increase of its size in new-born children, and its persistence to the fifth, sixth, or seventh year, or even to or beyond the age of puberty. Its abnormal enlargement is almost entirely restricted to children in whom we simultaneously observe a great predominance of the whole lymphatic glandular system, rachitis, and hypertrophy of the brain. It presents either two lateral, flattish, round, thick lobes, which descend on each side into the mediastinum posticum, or it forms a tongue-shaped mass which extends downwards on the pericardium, and rests on the right auricle. Whether the thymic asthma which has been recently described, and which occurs in delicate children, is actually dependent on the pressure of an enlarged thymus on the air-passages, or whether there is any essential connection between that disease and the thymus, are questions requiring additional observations and careful examination.