left brachium of the ferret, cranial to the left of the photo; lateral musculature

left brachium of the ferret, cranial to left of the photo; anterior and medial musculature

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

Introduction

The ferret is a quadrupedal, terrestrial animal. It can pronate and supinate the forelimb to some degree, but does not have the range of motion found in humans. The ferret is plantigrade and has five fully functional digits of the manus. The forelimb is not specialized for flying or for manipulating objects, and although the ferret is carnivorous, it does not use the manus to procure food. The radius, ulna, and humerus were approximately equal lengths. One noticeable characteristic of the limbs of the ferret was that they were short for their body length when compared to those of the fox and cat. Differences in limb proportion in these carnivores might reflect the various methods these animals use to catch their prey. Foxes and cats use their forelimbs to grasp prey, while the ferret uses its mouth and teeth to severe the spinal cord of its prey [1]. Ferrets are not cursorially adapted, and have short limbs, but flex and extend their spines in locomotion to increase stride length. Ferrets' short legs allow them to crawl through burrows in search of prey.

Adapted from Klingener (1979).

Dissection

We dissected the left forelimb. We had skinned the brachium during the dissection of the shoulder. However, fascia and cutaneous adipose tissue complicated the task of muscle delineation and had to be removed to access the underlying musculature.

The first muscle we found was the tensor fascia antebrachii, which extends the arm at the elbow. This muscle was extremely small and was superficial to the other muscles of the upper arm. This muscle was cut in order to reach the triceps and biceps. Once it was reflected, the triceps brachii, with its four heads, was visible.

The triceps brachii are the major extensors of the arm [2]. The angular, long, and lateral heads of the triceps were easily found because they were on the lateral aspect of the arm. The medial head, on the medial side of the arm, was more difficult to ascertain. It was identified based on its origin, the posterior surface of the humerus, and its insertion in the olecranon process with the other three heads of the triceps. The term "triceps", therefore, is a misnomer in the ferret because the muscle actually has four heads [2]. Mammals can have triceps with up to five heads. The fifth head, the anconeus, found in some mammals such as cats, is incorporated into the medial head of the triceps in mustelids [2]. The four heads of this muscle were of different sizes, with the long head being the narrowest and longest. The lateral and medial heads were approximately the same length and were shorter than the angular and long heads. The lateral head was significantly wider than all of the other heads.

The major flexors of the forearm are the brachialis and the biceps brachii [2]. The brachialis was found on the lateral side of the arm, while the biceps brachii was found on the medial aspect. The brachialis was lateral to the triceps and was significantly thinner than both the triceps and the biceps brachii. The ferret does not have a coracobrachialis muscle.

Locating the biceps brachii was difficult because it required that the arm be pulled back to expose the medial aspect. The biceps brachii in ferrets has only one head.

References

1. Fox, J.G. 1998. Biology and Diseases of the Ferret (2nd Ed.). Williams & Wilkins, Baltimore.

2. Klingener, D. 1980. Laboratory Anatomy of the Mink (2nd Ed.). William C. Brown, Dubuque, Iowa.

Links

return to Comparative Mammalian Anatomy home

return to Mammalian brachia

to ferret shoulder