When the Museum of Comparative Zoology opened more than 100 years ago with a small specimen collection kept in limited space and financed on a shoestring budget, few people could have predicted that it would become one of America's best natural history collections and one of the preeminent teaching and learning grounds for natural historians.

The museum keeps a low profile. It has its public side, with displays next to the glass flowers exhibit at the University Museum. The public museum contains a vast array of exhibits--from stuffed birds, mammals, and dinosaurs to exotic fishes, fossils and other creatures found by natural scientists. Although many children and adults wander about throughout the day, patrons only see a small part of the actual collection.

The displays the public visits are a small part of the entire complex of turn-of-the-century buildings behind the Science Center, on Oxford St. Almost half of one building is devoted to the scientific research collections that form the core and purpose of the museum. The side entrance is marked "Closed to the Public." Within those doors, students and professors have their offices amidst rows of cabinets which house large collections of animals that are seldom seen by visitors.

Within the giant cabinets that fill each floor of the building, scientists store collections of an incredible array of creatures, from the largest bird in the world to the smallest owl, fossils of the earliest known life or fossilized mammoths. In all, the museum houses collections of almost every historical precursor to men, including a marine biology section.

Most of the rooms in the museum smell of moth balls, alcohol and dust. By simply unlocking a cabinet, and pulling out one of the drawers, students can confront face to face a giant harpy eagle which eats 30 pound mammals.

Although he is stuffed here, the creature would otherwise be seen only in South America.

So the collection serves primarily not as a showcase for oddities and rarities but as a teaching ground for studying and observing animals before or after an expedition. Graduate students and professors in the museum have stories to tell about where they've gone to study and observe their particular fish, reptile, or animal. Some of them keep live specimens in their small offices, so walking into an office may mean being confronted with a room full of glass tanks of snakes or frogs.

"We are probably the best example anywhere in the country of this great integration between the museum function and the academic, teaching function," says James J. McCarthy, director of the museum. "Unlike any other Harvard museum, the activities are very intimately interwoven with the teaching functions of the department," he adds.

It's not surprising that many of the curators see the collections as akin to libraries; things are collected that might never be used but are simply preserved for certain classical traits. Like many libraries, the Museum has a rare books collection.

"Any scientific collection is essentially a library," says Ruth C. Turner, co-curator of the mollusk department. "The collection can give you enormous amounts of data."

"So these collections have become increasingly more important as animals become extinct or as environments change. We have things from Miami where now you see skyscrapers. As man alters the enviroment, the collections become more and more important."

"The collection is like Houghton [Library]," says Raymond Paynter Jr., curator of the bird collection. "It's full of treasures but its growth is very slow."

The bird collection ranks third in the country with about 350,000 specimens, Paynter says. Among these is a collection of Chinese birds that "are the best in the world, better than even China," he says.

Along with the Chinese birds are two great auks, an extinct relative of the penguin. "No other museum has more than one," Paynrwe says.

Where the bird collection is numbered by specimen, though, the invertebrate paleontology collection is quantified in tonnage or groups of fossils. This fall the department had to throw away almost 20 tons of fossils because they were taking up too much room and no one could catalogue them. Only four fossil collections surpass Harvard's.