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Wednesday, May 25, 2011

St. Albert and the Worm Dissection



Yesterday, we dissected worms as part of our St. Albert Science Class.

After starting with prayer, we sat down and discussed the various functions which animals have to carry out in order to live and thrive in this world. In brief, we talked about how most animals have to:

Move about
Make baby animals

Along with this short and incomplete list, I added:

Excretion or elimination of waste products
A nervous system to control all of these functions

All of these functions can be seen rather easily in the lowly earthworm, Lumbricus terrestris. Here is a picture of an earthworm in happier times:

This discussion superficially covered these functions mentioned above. The children were not as interested in 'functions of an animal' as they were keen on asking other questions, such as:

Is the worm still alive?
Could it come alive if we put it into the ground?
Do scientists and doctors dissect people?

Cadaver dissections is something I can talk about, and that started a HUGE side discussion. I told them a little about what it was like to dissect a human body in medical school. I explained where the bodies came from, how they were donated by people before death, and this was a tremendous gift they had done for the field of medicine. I mentioned that my cadaver in anatomy lab was a man with a tattoo of the name 'Ann' on one of his arms. I also mentioned that I pray for the repose of that man's soul whenever I think of him.

They wanted to know what it smelled like. I forgot to tell them that we wore clothes designated for anatomy lab and nothing else so they could be thrown out at the end of the semester. As I write this, I recall how it took a while to get the odor of formaldehyde out of my system after lab. Thankfully, our worms came in a different type of preservative which smelled bad, but not as awful as formaldehyde.

As an aside, I skipped over the fact that earthworms are hermaphrodites, where they have both male and female parts for making little worms. For the sake of this class, we considered this worm to contain 'reproductive organs' for producing eggs. Our children can learn the details of reproduction later.

Originally we were going to do the dissection out in the open air, but the wind was too strong, so we did it in the school room.

We prepared for the class by getting some thick cardboard to use as the dissection boards. We got out a container of surgical instruments and dissecting implements we had set aside for classes like this. Our older children had used them in the local home school co-op; Nathaniel assisted me and his siblings by showing them how to dissect the worm. I reminded them that scalpels and knives are used very little in dissection. This is why we could use one scalpel to dissect five worms; this made the class safer than if every child were waving around a #15 blade.

I had obtained the used surgical instruments not by theft but by getting broken instruments from the sterile supply department of one of the hospitals I worked at in San Antonio. At that time (1998), we were dissecting frogs, and I wanted some tools for the job. The head of sterile supply, once he realized why I wanted the instruments, let me look through a barrel full of hemostats, forceps, scissors, needle drivers and probes which were too damaged to be repaired or reused for surgery. They still could be used for frog dissection, though. We held onto those instruments for other dissection classes. The only thing I bought recently for dissection were some disposable scalpel blades.

We used non-sterile gloves bought at Costco. Max brought along his own device to limit the smell:

After pinning the worm to the cardboard and identifying external markings on it, we all made a small incision on the dorsum, or back, of the worm, and then used scissors to open it up for inspection. Here is where the pins really came into play:

Looks kinda gross, eh? The anterior, or front, part of the worm is where all the business takes place. After the first two or three inches, the body of the worm consists of repeating segments which only contain the digestive, excretory, nervous, and respiratory system. Muscles in the wall of the body help move it. For this reason, we did not fillet the whole worm.

The internal anatomy shows what the highest priorities are for a worm. The major system is the digestive system, which is the dark tube running the length of the body. At the front of the worm, the digestive system consists of a mouth, pharynx, esophagus, crop, and gizzard. I explained how the worm, like the chicken, has no teeth, and must find another way to grind up food. This led to a side discussion of the Thanksgiving turkey, and all the little bits of turkey which come in a little bag inside of it. I reminded them of the gizzard which the turkey uses to grind up seeds and grain, and how this is similar to the one the worm uses.

Some of the children looked uneasy. Perhaps we won't be having turkey this Fall....

The next biggest organ system are those for making little worms. In comparison, the brain is barely recognizable. It shows that worms spend very little time writing sonnets to their loved one or blogging about books they have read. Most of the white things in the picture below are for reproduction.

After cleaning up, we reviewed some of the functions of an animal, and how they are accomplished by the lowly earthworm. I also talked about how important worms are to our soil. Recently, I tilled the garden, and I only saw one worm in the soil. In the future we may be raising worms to help our North Texas soil grow more than just grass.

I don't think any of the children walked away from this wanting to go to medical school, but there is still time....

St. Albert, pray for us!

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