Diagnosis is simply ascertaining the nature of a morbid condition or disease under which a person may be suffering, by an examination of the symptoms present in the case. Diagnosis is by far the most difficult part of the practice of medicine. It is in this department chiefly that medicine derives great advantages from the collateral sciences, and it is chiefly in its relations to diagnosis that medicine may itself lay claim to being a science. The practice of medicine is certainly nothing more than an art, and a not very highly developed art at that. In difficult cases, the process of diagnosis requires of the medical practitioner the applica tion of all he has been able to learn by the most thorough and careful research, and, frequently, his own deepest personal insight into the nature and phenomena attending the manifestation of disease in its great diversity of forms. It will not be expected, of course, that every person can be made, even by the most useful helps, a skillful diagnostitian, and on this account, perhaps, all medical knowledge can never do away with the necessity for a skillful physician. In a large proportion of cases the most important work for the physician to do is to make a diagnosis, thus ascertaining what is the real condition of the patient, and, from this, reasoning back to a discovery of the causes of the diseased state, by the removal of which, a very large proportion of all cases may be brought to recovery, even without the application of any remedial measures whatever.