Drawing with Line Variation (The Skeleton)

Draw the human skeleton using principles of contour line drawing. Draw slowly with detail, using your eyes to follow the contours seen. Avoid drawing lines that aren't based on what you see or observe. 

Using a black ink pen or marker trace your drawing. Use line variation by making your line flow from thick to thin, thin to thick or some other variation. Try to enhance the illusion of depth with your line variation.