whether incorporeal, or an aura, or a breath, or some juice, or a certain motion, or an impulse, or something else, and in what manner it may be able to overcome the resistance of heavy weights, we shall see in its proper place. For now, it may suffice to conclude from the evidence of the senses only this: that the command of the soul’s motive faculty is carried through the nerves, without which voluntary motion cannot be effected.

Chap. 2. Description and use of the muscle:

On the Description and Use of the Muscle.

CHAPTER II.

Just as is customarily done in other physico-mathematical sciences, we shall attempt to explain this science of the movement of animals from phenomena as if they were foundations; and because muscles are the primary organs of the movement of animals, we shall first examine their structure, parts, and evident operations.

PROPOS. I.

A muscle is commonly posited as an organic part which consists of a tendon, a membrane, flesh, veins, arteries, and nerves. A tendon is found for the most part at the beginning and the end of the muscle, which seems to have a nervous consistency and to participate in the nature of a bone ligament. The tendinous beginning is called the head of the muscle, the end the tail, and the intermediate part is called its belly, which is filled with muscular flesh. They think that this does not properly constitute the muscle, but rather brings about its convenient consistency by filling the interstices of the fibers and, in a certain way, encrusting them,