A medical encyclopaedia is a comprehensive written compendium that holds information about diseases, medical conditions, tests, symptoms, injuries, and surgeries. It may contain an extensive gallery of medicine-related photographs and illustrations.  A medical encyclopaedia provides information to readers about health questions. It may also contain some information about the history of diseases, the development of medical technology uses to detect diseases in its early phase. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions.
Four major elements define a medical encyclopaedia: its subject matter, its scope, its method of organization, and its method of production:
A.D.A.M (Animated Dissection of Anatomy for Medicine) contains thousands of articles discussing diseases, tests, symptoms, injuries and surgeries. Content is reviewed by physicians; the goal is to present evidence-based health information. It also contains an extensive library of medical photographs and illustrations. MedlinePlus is a free Web site that provides consumer health information for patients, families, and health care providers. MedlinePlus brings together quality information from the United States National Library of Medicine, the National Institutes of Health (NIH), other U.S. government agencies, and health-related organizations. The U.S. National Library of Medicine produces and maintains MedlinePlus.
WebMD is an American provider of health information services. It is primarily known for its public Internet site, which has information regarding health and health care, including a symptom checklist, pharmacy information, blogs of physicians with specific topics and a place to store personal medical information. The site was reported to have received over 17.1 million average monthly unique visitors in Q1 2007 and is the leading health portal in the United States. The site receives information from accredited individuals and is reviewed by a medical review board consisting of four physicians to ensure accuracy.
Medscape is a professional portal for physicians with 30 medical specialty areas and over 30 physician discussion boards. Recently WebMD has been acquired by the News Corporation.
MedicineNet, Inc. is owned and Operated by WebMD and part of the WebMD Network emphasizing non-technical, in-depth medical peer-reviewed information for consumers. Founded in 1996, WebMD acquired MedicineNet in 2004. MedicineNet, Inc.'s main office is in San Clemente, Calif., and the corporate office is in New York City.