Dissection of the Cat I: Skinning
At the University of Cincinnati Clermont College, the cat is used as the dissection animal to teach anatomy in our Anatomy and Physiology courses. There are several reasons why this choice of dissection animal has been made. First, the cat’s anatomy is similar enough to human anatomy that the majority of anatomical relationships can illustrated using this animal. Second, the cat is large enough for its features to be clearly distinguishable to the student. Fetal pigs, which some institutions use, are small for this purpose. Third, the physical act of dissection is an extremely effective learning tool in contrast with “virtual dissections” available in computer programs. Fourth, cats are plentiful and inexpensive enough so that each team of two students has the personal hands-on experience of the dissection. The question of the ethics of using cats for this purpose can and should be raised. See the bottom of this page for a discussion of this ethical question .
The following are the steps to the proper and orderly preparation and skinning of the cat to optimize its use for dissection throughout the rest of the year. At the conclusion of this and each dissection, thorough cleansing of instruments, desks, sinks and floors is extremely important. Please be rigorous in your cleanliness. Use a sponge for all steps of cleansing except the very last. Use a single paper towel to finish drying the cleansed desk.
1. LABEL BAG WITH YOUR TABLE NUMBER: Place bag on a clean table with the end you will open to the left (the end with the larger margin of plastic beyong the heat seal.) Attach a large label at the lower right of the bag with your table number and class hour written in large black marker letters. Fold it over so that the number is visible on both sides of the bag.
2. DRAIN THE FLUID: At the sink, with rubber gloves, carefully cut open plastic bag close to the heat seal (so that it can be securely closed when finished). Remove cat tail first into the sink so that excess preservative fluid drains away. Squeeze out excess fluid from the cat’s fur by milking down from head to tail. Set aside the bag, keep its outside clean and free of embalming fluid and cat parts…
lines to cut
3. LIE CAT ON ITS BACK on your desk. These cats have been injected with color coded latex: red for arteries, blue for veins, and yellow for the hepatic portal system. Note the three latex injection sites: 1) at the neck, 2) in the inner R thigh, and 3) in the right lumbar region of the abdomen. Try to include these cuts in the lines where you make your incisions. Before you cut, make an illustration of the ventral view of your cat in your notebook with dotted lines showing where you are going to cut. (Again, what do the three colors of latex indicate?)
4. CUT ALONG THE VENTRAL MIDLINE, THEN ALONG VENTRAL SURFACE OF THE LIMBS: Lift the skin just below the xiphoid process, snip a shallow cut with scissors. . Insert the rounded tip of the large scissors under the skin at the cut, lift the skin and extend the cut up to the neck, and down to the pubic bone, stopping just above the . Continue the cuts down the medial surface of each thigh to the anterior-surface of the leg, and out along the anterior surface of the forelimbs all the way to the dew claws . Extend the ventral cut anteriorly through the neck incision to the right corner of the mouth.
5. CAREFULLY TEASE THE SKIN AWAY from the underlying muscle (or bone) with a blunt instrument (fingers and thumbs work well). The cottony material which ties the skin down to the body is called superficial fascia. Watch the skin so that you leave all tissue on the body. If you come to a difficult area, work around and behind it for a better approach. Here are the problem areas to which muscle may adhere to the skin: 1) the flanks, 2) the neck, 3) the shins, and especially 4) the head . Do not tear or remove underlying muscle, but note that force is occasionally needed.
6. CUT AROUND EITHER SIDE OF THE PERINEUM TOWARD THE TAIL. Cut along either side of the genetalia past the anus. Then cut the skin between the tail and the anus to leave a ring of fur around the perineum (genitalia and anus). Make a cut along the ventral surface of the tail and peel back the skin down the tail. Continue skinning on the legs until the skin has been freed to the paws, cut the circumference of the skin around each limb. Take care not to cut the tendons of insertion in the wrists or ankles.
7 . SKIN THE HEAD carefully. After you cut to the R corner of the mouth, Peel the skin away from the base of the ears.
Feel for the base of the ears and cut through the auditory canal just above the base on upper side of the head. Leave muscles on the skull.
Peel the skin off the scalp until you feel the rims of the orbits . Pull on the pelt to show white cottony fascia over the eyes. Carefully and slowly release the fascia with light scalpal cuts. Leave the eyelids on the pelt.
Cut close to the bone to separate lips from upper and lower jaws.
Leave the entire nose on the pelt by cutting deeply into the flesh of the nose after the skin has been peeled away everywhere except the nose.
8. PUTTING IT AWAY: Wring out the pelt once more. To store your cat, pull the skin over the nose, wrap in proper position, place wrapped cat in the plastic bag, fold the bag longways and press out the air. Then twist the end, fold it over, and secure with 2 or 3 turns of a heavy rubber band. If you do not fold it, the juice will leak out into the box of cats… Place in the storage box so the numbers are in the right front corner so that it is easy to locate your cat for the next dissection.
9. CLEAN UP!! Wash dissecting tools thoroughly, dry them with a single paper towel, replace in the kits, and return to their proper location in the storage box. Clean up all fur, fat, and stray pieces from your desk, floor, sink and surrounding counter. Wash all surfaces and edges thoroughly with a sponge dipped in soapy water, picking up all hairs, and removing grease. Finally wipe to near dryness with a well-rinsed, wrung-out sponge. (Please do not waste paper towels for this step.)
THE ETHICS OF USING CATS FOR MEDICAL SCIENCE DISSECTIONS
The question of the ethics of using cats for medical science dissection and learning can and should be raised. The ethical argument against the use of cats would be stronger if cats were bred specifically to be killed for dissection. However, the cats we use are the product of uncontrolled reproduction of pets. The surplus wind up at the animal shelter. At the animal shelter, the majority of cats are “euthenized” in a hypobaric chamber. In this chamber, the air is pumped out until the animal first passes out, and eventually dies of oxygen starvation. In the great majority of cases, the carcasses are then either cremated or buried. It is clear that using these animals which have already been euthenized yields at least one positive outcome of their sad deaths, one of advancing the teaching of medical science. Until the pet population explosion is under control and there is no surplus of euthenized cats, it would seem that a constructive use of a social tragedy is to be encouraged.