What is a glucunculus?  A glucunculus is distorted drawing of the human body showing the relative size/proportion of the organs based on the amount of glucose that each organ uses.  The glununculus is based on a similar type of drawing, called a "homunculus" that shows the parts of the human body as relative to the amount of your brain that is devoted to that region.  A homunculus is shown below. 

These diagrams are meant to show that a large area of your brain's cerebral cortex is devoted to your hands (particularly your fingertips), mouth, nose, etc, due to our senses.