I always love finding old anatomical drawings and diagrams, but what completely sold me on this one is the perfect heart shape at dead center, portraying the sacrum of the skeletal system (which does have a sort of heart shape to it but it feels almost as if the Marcia Hoyle who drew this decided to exaggerate it and use it at the anchor to draw out from.) Who knows, but it makes me glad (feeling almost like a stealthy insertion), and the rest of drawing does too, executed largely in dark blue colored pencil, but with black outline to the body and red, yellow and green accents, quite nice at the knees. Signed at lower right. 

18" x 12" and in good vintage condition, on good weight cream paper, with a few light creases along the top and to bottom left corner.