what has been seen ...

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What could have been so bad for Madame Henry Fouquet's dog that he looks so appalled?

Perhaps he didn't care for the painter?  That would be odd, for Charles Auguste Emile Durand - better known as Carolus-Durand - made his living painting Parisian high society in the mid to late 1800's.  Many of these portraits include dogs, often relaxed to the point of slumber.  Not this one.  Ah well, you can't charm every dog every time.  ("Portrait of Madame Henry Fouquet," 1876.)  By the way, if you caught yourself thinking either "Wow, that looks like a Velasquez," or "Wow, that feels like a Sargent," you were right.  He studied the first, and had the second as a student.