Blood and Guts is a great book for 9 to 12 year olds to study human anatomy and physiology. It's inexpensive, fun, and filled with all sorts of activities, like a cow's eye dissection. Today I dissected cows' eyes with a 10 and 11 year old, who have been using Blood and Guts for science this past year, and two 8 year olds (one of which was my son) that happened to be interested. This is an easy and inexpensive dissection for beginners since most parts are very easy to identify and not very delicate. You can get everything you need from Home Training Tools (see links section) including the eyeball and guide, though we found a way to save some money. I suggest you get the dissection kit and tray, costing $15 combined (these are reusable) from HTT. You can throw in the eyeball for an additional $2.50 or you can, like we did, call a local slaughter house and get them for free. The fall is the best time when the slaughter house is the busiest--we were lucky to get 4 over two days this week. Since they are fresh you don't need to worry about any formaldehyde or it's accompanying smell. Dissection guides are readily available for free online. Here's just one:
The kids all did a great job, and the dissection helped the older kids to better understand and remember the anatomy and even some of the physiology. The mess wasn't too bad to clean, either.