First written in 1919, this is a text on using the eye as a diagnostic tool, with the belief that it reveals abnormal conditions and changes in every part and organ of the body. This science enables the diagnostician to ascertain, from the appearance of the iris, many of the patient's inherited or acquired tendencies toward health and toward disease, his condition in general, and the state of various organ's in particular. The author also contends that the diagnosis from the iris of the eye positively confirms Hahnemann's theory that acute diseases have a constitutional background of hereditary or acquired disease taints or systemic encumbrances.