The biceps brachii or simply biceps is a muscle in humans and other quadrupeds. Using the elbow the muscle helps the movement of the forearm. In humans, the muscle is more complex, and allows more complex movement than in other quadrupeds. The word biceps literally means two-headed, and refers to the fact that the muscle attaches to two different parts of the shoulder. In that part of the shoulder, the Musculus deltoideus lies above the attachment points, so this cannot be seen easily.
In quadrupeds, the muscle only attaches at one point of the shoulder. To be able to compare the anatomy, it is also called biceps.