Chapter XV.

1. Concerning marrow, for this is one of the fluids which exist in some animals. All the natural fluids of the body are contained in vessels, as the blood in the veins, and the marrow in the bones, and others in membranes, skin, and cavities. The marrow is always full of blood in young animals; but when they grow older, in the adipose it becomes adipose, in fat animals fatty. There is not marrow in all the bones, but only in those that are hollow, and not even in some of these, for some of the bones of the lion have no marrow, others but little; wherefore some persons say the lion has no marrow at all, as was before observed. In the bones of swine there is very little marrow, in some none at all.