Before you go, I'd like to make a couple of personal comments about dissection and then I'll answer some of the typical questions I get from students.

There's no questioning the fact that dissection in schools has an impact on animal use. All of the specimens and even many microscope slides (ie. animal tissues) came from once-living animals. Whether the animal died at a factory farm or whether it was put down at a pound or shelter, these are real animals.

You should have a choice in deciding whether to dissect or not. But if you do, please do it with the utmost respect for the animal before you.

Q. What will I be dissecting this year?
In a typical Ontario high school under the new science curriculum you can expect to first dissect in grade 11 biology. Beyond or before that things vary.

For example, I've taught dissection of the frog and flower in grade 9 science, the earthworm, perch, and owl pellet in grade 10 science, the sheep heart and fetal pig in grade 11 biology, and the sheep brain and pig kidney or squid in grade 12 biology. I don't do them all every year, however.

Q. Do the specimens smell bad?
Not really. For the most part it's the preservative that gives an odour. The specimens themselves are actually pretty sterile because of the preservative. I suggest if you find the odour bothersome that you breathe through your mouth when you have to get close. It's also a good idea to wear safety glasses of some kind to protect your eyes from the preservative.

Q. Do the specimens bleed?
No. All blood has long-since been removed or has hardened so it's not going to spray out at you. The fact that the blood has hardened is helpful in that it makes blood vessels a bit tougher so they are less likely to break during dissection.

Q. Why didn't my teacher give me a scalpel?
Because your teacher knows better. So many dissections don't require a scalpel and would probably be ruined by an inexperienced user. Usually you'll use scissors to make incisions in the skin and a combination of scissors, forceps, probe, and FINGERS will do for the rest of the dissection. Please don't reach for a scalpel when you can use something else.

Q. Should I wear gloves?
Yes, you should. I've done tons of dissections without them but I suggest you wear gloves. Your hands will still feel and smell a bit funny. Wash frequently with soap and in a few hours your hands will be back to normal. It's all part of the dissection experience so don't sweat it.

Q. Can you help me find the aorta?
No problem but do you have your lab manual or dissection guide at your lab bench? Do you know where the aorta should be, where it comes from and where it goes? I'll be happy to help you if you are prepared to do some groundwork.

Q. Can I bring in a digital camera?
Absolutely. I know I will. Taking your own photos will definitely help you with your studying and if you get some good shots I might feature them on zeroBio. I'm also interested in exploring dissection animations and video so perhaps you have some expertise in those areas?

Q. Can I name my specimen?
Please don't. Although you probably have the best intentions, for the most part I think it's unnecessary and borders on disrespect. Best to call things what they are and act accordingly.

Q. How should I study for the dissection test?
Chances are you will have to write a dissection "bell ringer" during which you will rotate around the room from specimen to specimen answering questions. There will be a time limit, hence the term "bell ringer" (often there's no bell; just me saying "next"). As a general rule for the classes I teach, all the structures you will be required to know are labelled in the slideshows here in the Dissection Lab.

Q. Can you share some tips on dissection?
I'm glad you asked! To get the most from a dissection, you will have to ignore what your nose is telling you and concentrate on what your eyes are seeing. You'll definitely need to use diagrams or lab manuals to help you locate some structures. You see the trick is that you don't need to know a ton about anatomy ... but you really need to know how to use reference materials.

Imagine that your dissection is like driving to Florida for summer vacation. You need a map, right? While the map is not an actual photograph of everything on the highway, it's enough of a guide to show you major landmarks and by constantly refering to the map, you can find your way to Florida. So now, when you dissect, you need a manual or diagram right there beside you and if you constantly refer back to it just like a map, you'll find the major structures and can use these to locate everything else.

Now even if you know your way around, that doesn't mean that you should make your initial incisions casually. Think about the organs lying just under the skin and shun the scalpel if you can. For many small specimens, you should lift up the skin with forceps or fingers somewhere down between the legs and insert the sharp end of scissors just under the skin. Then start cutting upwards to a point midway between the arms. Next, cut towards the back (dorsal side) of the specimen under the arms. Do the same above the legs and you'll now have a flap of skin on the left and right. Make sure the flaps are cut cleanly from the middle of the body as far towards the back as possible and then pin the flaps to the dissecting tray.

If you've made a shallow cut, you'll only have opened the skin at this point and you'll be looking at another layer which is muscle. Repeat the procedures above using the forceps and scissors but now be very aware that you are closer to the organs so insert the scissors and make your cuts very carefully so as not to hit the organs below. If you do hit an organ (happens far too frequently), some liquid may spill out and make it very difficult to see anything. In that case, don't panic -- just hold the specimen in the dissecting tray under the tap and wash out the area. You might need to do that washing a few times, even when you are well into the dissection.

Assuming you made it through the skin and muscle, you're into the body cavities. From here on, you'll be investigating the inner world of the organism. Do this gently by pushing organs aside with the blunt probe and especially with your fingers (wear gloves!).

Usually the major organs like the stomach, intestines, liver, and heart are pretty easy to spot. That'll obviously depend on the size of the organism and it's anatomy -- an earthworm's internal organs differ quite a bit from those of a fetal pig. Anyhow, the hard part of the dissection is looking for the smaller organs like spleen, pancreas, lungs, ovaries. Once again, consult a diagram or photo so that you know what you're looking for and then push stuff around, lift it up, clear out fat ... until you find it all. Kidneys are tough to locate because they're often almost completely hidden under a thick layer of fat deep in towards the dorsal (back) side.

But the hardest structures for most students are the blood vessels. For the fetal pig: start close to the heart with the major vessels such as the aorta. If your specimen is double-injected, the arteries will be red and the veins will be blue. Find the aorta and use the forceps or needle probe to CAREFULLY remove tissues surrounding it. Work your way up the aorta to the carotid arteries which go up the neck. Clear out the area around the carotids and then do the subclavian arteries which branch off the aorta and go into each arm. All of these are rather large vessels but dissecting them out without breaking them is a skill that takes practice. You absolutely must have a working knowledge of how these vessels connect to eachother and a diagram right beside you to refer to. After that, it's just like following a map but you need to take your time and be thorough.

Now about the brain ... the answer is generally going to be "no". The brain of a frog or fetal pig, as you know, is encased in bone. You've probably had enough trouble dealing with skin and muscle let alone the idea of tunneling through the skeleton. It's possible that shards of bone can break off and injure your eyes so the brain dissection is not without some risks. And it's not part of the grade 9 or 11 curriculum so it's out. I've taught at a school where grade 11 biology students dissected the fetal pig and the heads were saved for grade 12 biology to dissect in the Nervous System unit. Nowadays for grade 12 biology I just order sheep brains themselves. So use YOUR brain to concentrate on your assigned structures and leave the specimen's brain alone.

Q. What should I do now?
Well, now that I've talked a little about the ethics of dissection, incisions, and major and minor structures ... go and look at the slideshows. As you do, think about what you've read here and notice the quality (or lack thereof) of the dissections which were all done by students. Look at where the organs are located and what is around them. Think of the surrounding structures as landmarks to help guide you. Notice if the structure appears easy to spot or is it embedded in fat or encased in a sac? Before I forget, determine what organs are close to where you will be doing your initial incisions and remember them when you first start to open up the specimen.

So good luck and have a successful dissection!

High school biology website with flash animations. Requires current Flash player.