Most jarring to my modern sensibilities is that symptoms are given equal billing with well-defined diseases, as if symptoms alone were what doctors treat. By 1899, the Canadian physician Sir William Osler had introduced bedside clinical diagnosis to the American medical mind. Anyone from a charlatan to a homeopath can treat a headache, but it takes a doctor to determine whether the headache is caused by a migraine, a subarachnoid hemorrhage, or meningitis. The treatments for each condition have nothing in common, though the symptoms may be almost identical. What separates us from the dark ages is diagnosis, our ability to ferret out the underlying causes of symptoms, to resist being suckered by the superficial manifestations of disease.
Symptoms provide the clues that lead to diagnosis.
Diagnosis dictates treatment. The mind that skips the middle third belongs in the nineteenth century. The real trigger for the prescription is the cough, a symptom. It's the same with kids and fevers. Half the antibiotics we modern docs prescribe are as laughably worthless as the nux vomica used 100 years ago.