Last Thursday, I had my first lab for my Mammalian Neuroanatomy class. We got some human brains to look at, touch and play with a little, and then sheep brains to begin the dissection. Well, it was mostly preparation because it was the first day. We cut off the dura mater (the outer meninge, or membrane, that covers the brain/spinal cord), and took a peek at the pineal gland (in olden days, the purported seat of the soul) before returning the brains.
The term dura mater literally means "tough mother", and it really is a tough mother of a membrane. The pia mater, the innermost of the three layers, is soft and sticks to the brain. The arachnoid mater is a spider-webby network of membrane in between the two, through which cerebrospinal fluid (CSF) flows. But the dura (from what I could tell through my gloves) feels a bit like tightly woven cloth, and is not very stretchy.
See that stuff peeled off to the side and labeled "1"? That's the dura mater. That's really how thick it is.
The dura dives into the gap between the two hemispheres of the cerebrum with a clever little move called the falx cerebri ("4" in the above picture). In the human brain, the separation goes quite deep, but even the millimetric depth of falx cerebri in the sheep brain made it extremely difficult to cut (it was hard to get the scissors under it without poking into the brain tissue).
All in all, it was a pretty cool lab, except for the pungent odor of formaldehyde. We didn't realize just how thoroughly we had to wash our brains to get rid of it before we began, and fumes from the remaining formaldehyde stung our eyes whenever we leaned in for an extended period of time. That of course meant three out of every four minutes, because our tasks involved things like identifying tiny little cranial nerves and cutting off the dura mater while sparing as many of those tiny little cranial nerves as possible.
Don't worry though, my dearies. That was only because we didn't prepare well enough. Next time, the brainwashing will be complete! Muahahaha!