Most of the “higher animals” have body plans very much like that of humans–four limbs, a head on top with two eyes and two ears, a torso with chest and belly, etc. We can expect that the more an animal is like us on the outside, the more it will be like us on the inside, too, and by dissecting another mammal or even a bird, we can gain a decent idea of what we ourselves are like on the inside.
Chicken wings are cheaply available at most meat counters, and provide a nice analog to a human arm. Assuming you can find whole wings (not “party wings” or wing sections) then you discover three sections to the chicken wing, roughly in the same way that the human arm has an upper arm, forearm, and hand. The wing tip even has an “alula”, which looks somewhat like a bird’s version of a thumb.
More remarkably, if you feel for the bones through the flesh, you may discover a single large bone in the “upper arm”, resembling the human humerus, two long bones in the “forearm”, resembling the human ulna and radius, and several smaller bones in the “hand”. Given the similarity in bone structure, is there a similarity in muscle and tendon arrangement too? Will there be two big muscles on the front and back of the “upper arm” that bend and straighten the “elbow”, like the biceps and triceps muscles in humans? Will there be a bundle of muscles in the “forearm” that move the “hand”? It is easy enough to remove the skin from a chicken wing, observe the muscles and tendons directly, and find out.
The tricky part is to remove the covering of skin without damaging anything underneath. It is loose in most places, so it peels up fairly easily. But it isn’t completely free, either. It is stuck down tight to the bone at the trailing edge of the ulna, it is stuck pretty firmly around the hand, and elsewhere it is interconnected with the muscles with an interwoven network of “fascia”.
In very rough terms, you need to peel the skin off of the muscles and other fabric underneath, starting with the cut end and working your way out towards the wing tip. Exactly how you do this is a matter of technique. I have done it with a scalpel and dissection scissors, but I think it works just as well with a simple pair of kitchen shears. You can loosen the skin and free it from the underlying material by inserting the blade sideways between the skin and muscle, and working it gradually side to side, forcing it between the skin and underlying tissue. You then cut the skin and pull it off in strips by hand, and begin the process again, working your way in steps outwards towards the tip. I have also used a scalpel to cut and scrape the skin free from the material underneath, but in general, I think tearing works better than cutting. The connective fabric tends to tear most easily between skin and muscle, which is what you want, whereas a scalpel cuts whatever it touches. Chicken wings are quite cheap, so you may want to practice the dissection several times. (Incidentally, I’ve never tried thawed frozen wings, so I have no idea if they work as well as fresh wings.)
With a little care and practice, you should be able to remove most of the skin on the “upper arm” and “forearm”, and some of it around the “wrist” and on the “hand” as well. Here is an example of a wing I have (mostly) skinned:
The “upper arm” does indeed have two large muscles, one on the inside of the “elbow”, and one on the outside, each with a tendon running to the “forearm”. When you pull on each muscle, you will find that it does a job corresponding to the biceps and triceps in the human arm. If you pull on the biceps, it will fold the elbow, and if you pull on the triceps, it will straighten the elbow. Furthermore, the “forearm” has a bundle of muscles, with tendons running into the “hand” that make the hand move, just as muscles in the human forearm work the human hand.
Once you are done examining the muscles of the arm, you can trim them from the bones and reveal the skeleton underneath:
As long as you are playing with a chicken wing, here are a few more observations you may want to make, especially with the bones: If the butcher has sawn off the top end of the “humerus”, you should be able to see spongy bone (also known as cancellous bone) within the bulb on the end. If he hasn’t, you will see the rounded end intact and be able to observe the covering of cartilage. If you scrape the side of a bone, you may find a thin but tough fabric coating it–that’s the periosteum. If you break one of the bones in the middle (the thinner “forearm” bones are easier), you will find that it is hollow with a red pulpy “cranberry jelly” inside–that’s marrow, contained within the medullary canal. If you break open the “elbow” joint, you should be able to observe the slick cartilage that covers the bones where they meet and makes them slide smoothly over each other.
(Why is it so hard to break open the joint? Because of the ligaments binding the joint together. Unfortunately it is hard to get a good look at the ligaments in isolation, because the entire joint capsule is a cobweb of tough inter-grown tendons and ligaments. It is very difficult to remove the tendons without also removing the ligaments. Boiling helps to remove flesh and clean the bones, and may be a good way to discover the fine bones in the “hand”, but it removes the ligaments, and does not leave an articulated skeleton.)
If there is a correspondence between the parts in a chicken wing and those in a human arm, is there also a correspondence between the chicken leg and a human leg? To find out, we’ll have to dissect a chicken leg.