Louis XVI as the Benefactor of Surgery by Esprit Antoine Gibelin, 1771-1774, the Met
Just getting started? These academic art dictionary and encyclopedias are great sources for trustworthy information when first researching an artist, a medium, or a time period.
When analyzing a work of art, it's helpful to develop and apply a list of relevant questions. Consider:
Barnet's A Short Guide to Writing About Art provides many useful examples of analytical questions and is a required/recommended text for most Art History courses.