Well I'm not going to say that dogs do not cry tears from sadness but I will say some dogs just have runnier eyes. My little Sugar has runnier eyes than Spike and Gracie and I can assure you that he is in no way a sad baby.
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"If you have men who will exclude any of God’s creatures from the shelter of compassion and pity, you will have men who will deal likewise with their fellow men." — St. Francis of Assisi, 1181-1226