Working Like A Dog?

I am back at my job as the bookkeeper for a local Denver bookstore chain, working extra hours in the evenings and on the weekends, playing catch up.  I wouldn't say I am working like a dog, but then again, just how hard does a dog work these days? The one in the photograph above taken during my lunch hour sure wasn't working very hard, unless you consider begging for food work.  The phrase evidently comes from the time when farm dogs allegedly worked from sunrise to sunset, but what exactly did they do on a farm?  Plant corn? Milk the cows?  Most likely it is just more propaganda from the ASPCA.