Art academies were about copying casts, for the longest time. They were about learning the idealizations that past artists had already discovered were beautiful.
Reverse-engineering the volumes as Bridgman must have intended them, as I am doing here, is, frankly, a fun exercise. Your first instinct is to copy his lines, but they are regularly a bit off from the ones that would form simplified volumes.
I haven’t seen anyone else do these “hey, this us what Bridgman probably meant with his sketches” volume breakdowns. Has anyone else seen those? Because it is gospel that you should know your anatomy first before trying to read and decode his sketches. But has anyone made a book where he decodes Bridgman’s sketches? An annotated Bridgman would be useful, or not?
At any length, they are great for drawing from memory exercises, because they are relatively small, simple drawings which you can draw in minutes, and which highlight some aspects of anatomy worth memorizing. And I find them pretty.
Drawing from observation and drawing volumes from memory inform each other. To be able to draw from memory, it helps if you practice drawing from observation. But when drawing from observation, it helps if you can decode the underlying volumes of the thing you’re looking at.