His principal work is a Treatise on the Pathology and Therapeutics of Internal Diseases, in twelve books. The first eleven books were evidently material gathered for lectures or teaching of some kind. The twelfth book, in which considerable use of Aetius' writings is made, was written, according to Puschmann, toward the end of Alexander's life, and was meant to contain supplementary matter, comprising especially his views gathered from observation as to the pathology of internal diseases. A shorter treatise of Alexander is with regard to intestinal parasites. There are many printed editions of these books, and many manuscript copies are in existence. Alexander was often quoted during the Middle Ages, and in recent years, with the growth of our knowledge of medical history, he has come to be a favorite subject of study. Alexander's first book of pathology and therapeutics treats of head and brain diseases. For baldness, the first symptom of which is falling out of the hair, he counsels cutting the hair short, washing the scalp vigorously, and the rubbing in of sulphur ointments. For grey hair he suggests certain hair dyes, as nutgalls, red wine, and so forth. For dandruff, which he described as the excessive formation of small flake-like scales, he recommends rubbing with wine, with certain salves, and washing with salt water. He gives a good deal of attention to diseases of the nervous system. He has a rather interesting chapter on headache. The affection occurs in connection with fevers, after excess in drinking, and as a consequence of injury to the skull. Besides, it develops as a result of disturbances of the natural processes in the head, the stomach, the liver, and the spleen. Headache, as the first symptom of inflammation of the brain, is often the forerunner of convulsions, delirium, and sudden death. Chronic or recurrent headache occurs in connection with plethora, diseases of the brain, biliousness, digestive disturbances, insomnia, and continued worry. Hemicrania has its origin in the brain, because of the presence of toxic materials, and specially their transformation into gaseous substances. It also occurs in connection with abdominal affections. This latter remark particularly is directed to the cases which occur in women.