So now let's look at a part of the skeleton that's cylindrical. We're going to look at the left leg at the upper leg bone, thigh bone or femur. So let's start off by thinking about what we know about the cylinder. It's going to be a background and against the background. We'll have a highlight. Now in this case the cylinder isn't sitting straight up and down. It's a bit of an angle. So as I take my softer eraser and erase in a highlight I'm going to have it come down a bit of an angle to kind of match the femur. And then the light's coming from above on the side. So when it gets to the fattest part of the femur, the part that's closest to us, it has to travel in a straight line and can't bend around to the side. So there's a shadow there. So we'll put that in. And there's a smooth transition because the femur is cylindrical. We don't want a harsh edge between the shadow and the highlight. So I'm going to experiment with different ways of softening the edge, blending the edge. Now the femur's a little bit of an irregular shape. So I'm going to try and capture a little bit of that. I'm going to notice that it's a little wider in some places and that it changes direction a bit. When we get down here into the knee, for example, it flares out quite a bit. When we get up here, closer to the hip socket, there's some different structures that poke out. These are places of attachment points for muscles. And the head of the femur, the very top, is actually a kind of an avoid shape up here where you're hip joint. So now I'm going to work in some more details of the light and shadow. So I need the front and the femur to be bright so that it looks really bright. I'm going to darken the background a bit. I don't really want to dark wine here. Instead, I'm going to try to have an intermediate gray against the very bright area. And then the intermediate gray over here again against a much darker shadow area. I want the shadow to look like it's on the femur, not on the background. So I'm going to rub toward the center of the femur instead of rubbing into the background. Here the femur flares out, so the bright area flares out as well. And there's some interesting variations here where this attachment point comes out as a surface here that faces away from the light. Here under the ball of the femur. Because the bone is not a perfect cylinder, the way the bottle was, it has a lot of irregularities. We could start to put some of those details in. They're created, all these irregularities are created by the muscles and tendons that attach to your leg bone. So as I put more of these details in, I'll get a drawing that looks a bit more organic and natural. Down here at the bottom, we have a curve, just like we had on the curve bottom of our bottle. And I could develop more detail if I have the time and the inclination. But I think that that'll give us a basic idea of how to apply thinking about the light and shadow on the cylinder to a cylindrical part of the body. We have our dark, our light, and our background. We have our dark area, our light area, and our intermediate area.