[jfrancis]

The rib cage, along with the skull and the pelvis, is one of the important, fairly unchanging bony structures of the figure.

I have a bit of a hard time completely grasping the shape of its volume. Here's a bit of what I know about it.

The form is a lot like an egg with the top and bottom cut off.

The bones "sag" off of the spine so that the front every rib is lower than the back.

The first set of ribs is the same as the neck hole.

The spine seems fairly deep inside the rib cage because the ribs arch off the spine like valentine hearts, not simple hoops.

The ribcage is widest around the eighth ribs.

Here is a simplified approximation of the relationship between the spinal column and the rib cage as I understand it. It's not perfect, and the stripes are meant to convey surface information, not to be literal tracings of each bone. But I think it's a useful tool in grasping the rib cage.



If you can capture the spine and rib cage, and then hang the shoulder girdles (the scapulae in back and clavicles in front) off of it properly, you've gone a long way toward defining the form of the upper body.