Medical specialty dealing with the entire patient rather than a particular organ system, covering diagnosis and medical (rather than surgical) treatment in adults.
Its development began in the 17th century with Thomas Sydenham 's concept of disease, but until disease-specific therapies were developed in the 20th century, internists could do little to treat diseases. As more specific treatments became available, medical knowledge increased, and subspecialties in specific organ systems were defined, internal medicine became recognized as a specialty.