Natural Wonders

In Short

Natural Wonders is an introductory guide to general physiology written for young readers. Edwin Tenney Brewster leads children to examine how all living organisms—plants, animals, and human beings—share fundamental physical processes. Through accessible comparisons between living tissues and familiar everyday technologies, the book tracks how life forms eat, grow, move, sense, and defend themselves against disease. Brewster's text has endured because it treats children as serious thinkers, grounding complex biological concepts like cell structure, neural pathways, and evolutionary adaptation in direct, observable reality without resorting to patronizing sentimentality.

The Story

The book opens by laying out a unified foundation for biology, framing the central question: what do human beings share with all other living things, and how do they differ? Brewster begins with reproduction and embryonic growth, explaining that seeds, eggs, and human life all start from similar structural foundations. Whether examining a chick inside its shell, a bean plant packed inside a seed-case, or a developing fish, the book illustrates how living things draw upon stored nourishment—such as yolk—until they grow the necessary organs to feed themselves from their environment.

From early development, Brewster moves into the physical structure of living bodies. He demonstrates that organisms are not entirely alive; hair, nails, outer skin layers, and tooth enamel are dead structures that protect and support the soft, active "life-jelly" inside. This leads directly into the mechanics of animal instincts and behavior. Animals are born with innate drives designed to help them survive—such as a chick pecking at its shell or a kitten playing to protect its vital organs from potential predator strikes.

The narrative then expands into sensory perception and the architecture of the brain. Brewster explores how animals and humans interact with their environment through sight, sound, smell, and muscle sense. While humans rely primarily on visual information processed through localized brain centers, insects like ants navigate dark underground tunnels using intricate olfactory senses located in their antennae. Brewster demonstrates how human beings must build specialized neural pathways—such as speech and reading centers—through deliberate, hard practice, whereas animals rely more heavily on fixed, unchangeable instincts.

Next, the focus shifts to internal mechanics and biological chemistry. Brewster frames the living body as an engine fueled by sugar and oxygen. He explains how living organisms extract energy, process nutrients, and continually rebuild worn-out tissues by consuming other living matter. This physiological machinery leads into a discussion of health, sanitation, and immunity. Life is presented as a constant struggle against unseen single-celled organisms, flies, and disease-bearing pests, where white blood corpuscles act as an internal standing army that consumes invaders and clears away obsolete body tissues—such as a tadpole’s tail during its metamorphosis into a frog.

Finally, the book examines evolutionary adaptation, regeneration, and anatomy. Brewster details how embryonic cells can divide to form duplicated limbs or twins, and how simpler organisms like worms and lizards regenerate lost body parts. He compares animal features—such as horses' grinding teeth or cats' shearing jaws—to specialized tools shaped by natural forces over generations. Concluding with the grand scale of evolutionary history, Brewster shows how small, incremental modifications over vast stretches of time shaped modern species, leaving readers with a clear picture of the shared biological heritage connecting all living things.

How It Unfolds

The spark of life The book introduces embryonic development by showing how seeds, eggs, and animal young begin as small clusters of living cells attached to a supply of yolk or food. Brewster demonstrates that a bean seed is simply an egg with a tiny plant folded inside, waiting for the right conditions to expand.

Structures alive and dead Brewster examines the physical materials that make up living bodies, pointing out that much of an organism consists of dead material like hair, outer bark, or tooth enamel. These non-living layers serve as protective armor for the delicate, growing life-jelly underneath.

Instincts and physical play The narrative explores how young animals are born with automatic drives tailored to their immediate survival needs. A chick pecks instinctively against its shell to hatch, while kittens play-fight to practice protecting the ticklish spots on their bodies where vital blood vessels lie.

Building the human brain Brewster outlines how sensory inputs form physical networks within the brain, contrasting animal instincts with human learning. Children must actively construct their own specialized brain centers for reading, speech, and music through persistent daily practice and study.

Engines fueled by sugar The text turns to internal metabolism, describing living organisms as complex engines that burn sugar mixed with oxygen to generate movement and heat. Unlike man-made metal engines, living bodies use nutrient intake to continuously repair and rebuild their own internal machinery.

The internal army Brewster details the body's defense mechanisms against disease and pestilence, focusing on sanitation and cellular immunity. White blood corpuscles function as an internal standing army, devouring invading germs and clearing away unnecessary body structures like a tadpole's reabsorbed tail.

Tools shaped by time The final chapters cover anatomy and evolutionary adaptation, illustrating how animal claws, teeth, and limbs serve as highly specialized biological tools. Brewster shows how tiny, gradual changes over hundreds of generations stretched the elephant's nose into a trunk and shaped the distinct structures of modern species.

The People

Because Natural Wonders is a work of non-fiction, its central figures are the primary biological subjects, concepts, and scientific observers that drive the argument forward.

• The Child Reader: Framed as an active learner seeking to understand their place in the living world. The reader wants to know how their own body works and how they relate to other organisms; their main obstacle is the sheer complexity of physiological processes, which they overcome by performing simple sensory experiments and building neural pathways through study.
• The Life-Jelly (Protoplasm): The foundational substance of all living things, which drives growth, repairs damaged tissues, and powers bodily movement. Its main constraint is that it constantly wears out and requires fuel from external plant or animal sources; it ends up transformed into specialized organs or burned off as mechanical energy.
• The White Blood Corpuscle: The protective cellular worker within animal bodies. It wants to maintain internal order by devouring invading disease germs and clearing away dead tissues; its main challenge is repelling constant microbial attacks, and it ends up acting as both a defensive soldier and a demolition crew that recycles old body parts to build new ones.
• Charles Darwin and Scientific Researchers: The observing minds who systematically investigate the natural world. They want to uncover the underlying rules governing plant movements, animal senses, and evolutionary change; they face the limits of current human knowledge, leaving unresolved scientific mysteries for future generations to solve.

In Its Own Voice

“It is, in short, an attempt to lead children of eight or ten, first to ask and then to answer, the question: What have I in common with other living things, and how do I differ from them?”

— Brewster opens his preface by stating the core physiological question that guides every chapter of the text.

“Our bodies, therefore, and the bodies of all other animals, are gas engines, which burn sugar by exploding it mixed with air.”

— In explaining human metabolism, Brewster compares biological energy production directly to the mechanical workings of modern engines.

“In short, then, the animals haven’t different senses from ours, nor on the whole better ones. But they use them differently; and cultivate some senses which we let go to waste.”

— Analyzing animal behavior, Brewster emphasizes that differences in perception stem from adaptation rather than entirely different sensory organs.

What It's Really About

At its core, Natural Wonders is an argument for the fundamental unity of all organic life. Beneath its straightforward scientific explanations, the book examines how complex biological structures arise from simple, shared origins. Brewster challenges the rigid divide between humans, animals, and plants, demonstrating that every organism relies on the same chemical reactions, cellular materials, and evolutionary pressures. The text explores how physical form follows function, showing that behavior, instinct, and body parts are all practical tools shaped by environmental necessity. By explaining how human intelligence requires deliberate effort to construct neural connections, the book ultimately frames education and learning as a natural continuation of physical development, where mental discipline physically shapes the organ of thought.

Why Read It Today

Natural Wonders remains a remarkably charming example of early twentieth-century science writing that treats young readers with intellectual respect. Readers who appreciate historical science literature, clear pedagogical writing, or classic natural history will find much to admire in Brewster's crisp, logical approach. What makes the book memorable is its ability to translate technical physiological concepts—such as cellular metabolism, neural plasticity, and evolutionary change—into vivid, concrete mechanical analogies without relying on fantasy or oversimplification.

Modern readers should, however, be prepared for period-typical framing and dated scientific terminology. The text reflects the era in which it was written (1910), featuring casual racial comparisons of the early twentieth century, older medical assumptions regarding disease prevention, and dated phrasing around human genetics. Additionally, readers used to modern biological terminology will notice early industrial metaphors—such as comparing bodies to steam or gas engines. Despite these period artifacts, the book's core explanations of comparative anatomy, sensory mechanics, and biological adaptation remain engaging, clear, and remarkably insightful.