For comparison, see brachial dissections of a bat, a ferret, a fox, a rabbit, and a tree shrew.

Part I: Overview of arm

A cat is a digitigrade quadruped. It can both pronate and supinate its antebrachia. A cat has relatively short brachium and antebrachium for its body size, but they are strong and well developed. The antebrachium is longer than the brachium, which extends the stride length. A cat has bigger and stronger elbow extensor muscles than flexor muscles.
The skin of the brachium was removed by making extended incisions from the shoulder region to antebrachium. It is much easier to cut the skin off from the body, because the fur gets stuck to the muscles hindering a clear view.

Part II: Brachium (upper arm)

Elbow extensors:
· Triceps
-The long head of the triceps muscle originates from scapula, the lateral head originates from the proximal end of humerus, and the medial head originates from the three regions of the humerus from the proximal to the distal portion. They all insert onto olecranon and ulna near olecranon, and they extend arm.
-The long head and the lateral head of the triceps muscles are big and easy to find. The long and lateral heads are superficial muscles and are divided clearly even though they all insert in the same place. The long head is inferior and medial to the lateral head. The medial head is harder to find. In order to find the medial head, one must reflect the lateral head. As the name indicates, the medial head is located in the medial side of the body, deep to the lateral head. The medial head of the triceps muscle is a thin strip of muscle compared to the long and the lateral heads. Thus it does not act as a significant extensor of the arm as the long and the lateral heads of the triceps muscles do.
-The anconeus muscle originates from humerus and inserts on ulnar. It helps to keep the elbow joint firmly extended. Anconeus is a deep muscle, thus it is visible only after reflecting the lateral head of the triceps muscle. It is small and has a triangular shape. This muscle is located at the borderline of the brachium and antebrachium.

Elbow flexors:
· Brachialis
-It originates from the lateral surface of the humerus, partially underneath the acromiodeltoid muscle, and inserts onto ulna, partially covered by the brachioradialis. The brachialis muscle flexes the arm.
-This muscle is a deep muscle as it attaches to humeral surface, but it is not difficult to find this muscle. Although part of this muscle is visible on the caudal side from the lateral head of the triceps, in order to view this muscle clearly, the lateral head of the triceps muscle must be cut and reflected. It is one of the big elbow flexor muscles.
· Biceps brachii
-It originates from scapula and inserts onto tuberosity of the radius. This muscle acts to flex the arm.
-The biceps muscle in humans has two heads, but in the cat it has only one head. This muscle can be seen from the medial side of the arm. It is a deep muscle and lies close to the humerus. Thus it is only visible when the pectoantebrachialis muscle is reflected back. Once the pectoantebrachialis is reflected, it is clearly visible. This muscle is big, and thus a significant elbow flexor.
· Coracobrachialis
-This muscle originates from coracoid process of scapula and inserts onto the proximal end of humerus. It acts to adduct humerus.
-This muscle is very small and deep that it is hard to see. It is located medial and deep to the biceps brachii muscle. If the origin and insertion is followed, this muscle wraps around the humeral head. However, it is so tiny that it does not seem to have much action.