In college, the lab instructor pithed a frog and dissected it for the whole class. With great respect, he demonstrated the movement of food by the cilica of the digestive tract, the beating of the heart, and many other things. Apart from puns ("Boy, I'll bet that frog's pithed!") the entire demonstration was received with great respect.

ONE animal, its brain destroyed, demonstrated to 30 students many of the wonders of the living body. Whether or not this was ethical -- I don't know. I do know that wasn't done gratuitiously, with deliberate cruelty, or frivolously.