The appendix is part of both your immune and digestive systems. We do more with our appendix than dwarves do with their brains.
I just tried a terrifying forest. All was going relatively well at first. Dug a two tile wide moat leaving a 19x19 area inside it for my dwarves. While that was being dug out, one of my two marksdwarves ran north of the compound (pretending it was a military expedition) to bash a Giant Stoat zombie to death - he did it without getting hit at all. He didn't shoot because I forgot bolts (doh!) and hadn't cut down enough trees yet (the other wood went to a carpenters shop, a training axe (they were left with the crossbow bolts, apparently) and a wall to block of the currently frozen murky pool I accidentally dug into.
I removed all the outer ramps to try and keep stuff out, and that seems to have worked. Somewhere in there a nauseating ooze started raining. This was, apparently, some kind of minor blister or blood agent, as the dwarves exposed (all seven) started bleeding a bit but not enough to show up in either the thoughts or health screens. The miner moved to make an entrance down, while I queued up a few needed wooden objects.
Somewhere in there, the zombie crow men showed up. This was probably the beginning of slate, about the time the snow, but not the pond, melted. My two spears and two copper crossbow wielding militia beat down the zombies, and continued to do so for quite a while. But it was already spiraling down. I should have gotten stuff underground sooner. Somehwere in there, both speardwarves died, and hte rest were all running for their lives so I abandoned.
And so died Dyeraven.
Btw, two spears and two crossbows, with sheilds and mail (all copper) worked pretty well. It would have worked better with bolts. I only put two levels in skills. My other three dwarves were a diagonstician/mason, a grower/carpenter and a miner/stonecrafter. With slightly better embark items I think I might have been able to make it. Of course, I got extremely lucky in that the weird rain only inconvenienced me for the three months or so the fort lasted. I know it could have been worse.