veal stock. useless without the bone marrow?
Bone marrow is basically a fat. When you make a stock that includes marrow bones, then chill it to remove the congealed fat, the fat may well turn out to be mostly melted marrow. Bone marrow does add flavor to a stock, but bone marrow can also have a "minerally" flavor to it. Marrow is the part of the bones that manufactures blood cells, hence the mineally flavor. It can also make the stock cloudy, but almost all stock has to be well filtered to get it clear, so that's not a good reason for not using it. It boils down to (pun intended) personal preferences in the flavor profile you're after. When you want your stock to gel when cool, you do want a lot of "knuckle bones" with heavy cartilage; those "round smooth ends" of bones that are shiny. They are heavy with cartilage. So are chicken feet if you're making a chicken stock. And some combine chicken feet with veal knuckles to end up with a really nice demi glace after a whole lot of reducing. Oh, veal marrow will have a less minerally taste than beef marrow, however I haven't seen "real" veal in the U.S. in over fifty years, unless you raise and slaughter it yourself. In todays markets, upscale and downscale, what is marketed as veal is really baby beef. And as schoenfelderp states, the flavor in stock comes from the bones... and the bits of meat left attached to them. The basic difference between broth and stock is that stock should gel when chilled, broth shouldn't, but there are some "chefs" who would quibble.