The _physician_ might find, after asking a few questions and thus
making a diagnosis, that the patient had _La Grippe_, or _Pneumonia_,
or _Pleurisy_ (instead of merely a _cold_, as the patient _thought_).
The physician would find out what the patient _needed_, then write a
specific prescription-- and seldom the same prescription for any two
patients. For the requirements would always _differ_.
Or a man might have poor _eyesight_.
He might go to an _optician_.
Now, an _optician_ doesn't know much about _eyes_-- _he_ has made a
special study of _lenses_-- _he_ merely _fits_ glasses-- just as a
_druggist_ merely _fills_ prescriptions-- neither pretends to _diagnose_
or _prescribe_.
And an _optician_ is just as likely as not to fit a _near_-sighted man
with _far_-sighted glasses.
[Sidenote: A Truss Fitter Should Know as Much About Rupture
as an Oculist About the Eyes]