Headache, as a symptom of disease, is present in a great variety of conditions. It is nearly always present in acute fevers. It is also present in most organic diseases of the brain and spine, as well as in many affections of other internal organs, as of the heart, stomach, kidneys, liver, and reproductive organs. When present in connection with other diseases, it is sometimes the result of disturbance of the circulation incident to those affections, or it may be due to nervous sympathy. The following varieties of headache may be mentioned: