Compare the body axis of a four legged animal to the axis of a human

Humans are bipedal creatures and walk upright, the ventral surface is also the frontal surface, and dorsal surface is the posterior surface.  

However, the four-legged or quadrupeds, possess their heads at the anterior terminal and their tail at the posterior terminal. The ventral and dorsal surfaces are not posterior and anterior in the manner they are in humans.  

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