The Story of the Living Machine Informative Summary


This 1903 book, The Story of the Living Machine, by H.W. Conn, takes a revolutionary look at the living organism as a complex machine, building upon the foundational principles of evolution and the conservation of energy. Conn argues that many of life’s processes, including digestion, circulation, and respiration, can be understood through the lens of chemical and physical forces, just like the workings of a steam engine. However, he also acknowledges the limitations of this mechanical analogy, particularly when it comes to the intricate mechanisms of the cell and the enigma of mental phenomena.

Conn provides a detailed exploration of the cell, highlighting its vital components – protoplasm, nucleus, and centrosome – and their roles in processes like cell division and reproduction. He discusses the evolving understanding of protoplasm from a simple, homogeneous substance to a complex machine with specialized parts. Conn also examines the theory of evolution, emphasizing the importance of reproduction, variation, and heredity as the driving forces behind the gradual development of complex organisms from simpler ones. While recognizing the role of natural selection in shaping the fittest organisms, Conn also explores the influence of migration, isolation, and the direct effects of the environment on the evolution of life.

Key Findings:

  • The living body is a machine. While the body’s complexity surpasses man-made machines, it functions in a similar way by transforming energy from food into motion, heat, and other forms of energy.
  • The cell is the fundamental unit of life. It is a marvelously complex machine with specialized parts – protoplasm, nucleus, and centrosome – that contribute to vital processes.
  • Evolution is a gradual process. The intricate machinery of complex organisms like humans developed over millions of years through the accumulation of variations and the selection of the fittest traits.
  • The origin of life remains a mystery. Despite significant advancements in biology, the very first steps in the creation of the living machine – the cell – are still shrouded in obscurity.


  • The body is a sophisticated energy converter. Just like a steam engine, the body takes in energy stored in food and transforms it into various forms necessary for its functions.
  • The cell is a complex, intricate machine. It’s not a simple homogeneous substance but a complex entity with specialized parts that work together to carry out life’s processes.
  • Evolution is a slow, gradual process. It’s a continuous cycle of variations, selection of the fittest, and inheritance that shapes the diversity of life on Earth.
  • The origin of life is a fundamental scientific question. While much has been discovered about the mechanisms of life, the origins of the first living cell remain unknown.

Historical Context:

  • Conn’s book was published in 1903, at a time when the theory of evolution was still being hotly debated and the concept of the cell as the fundamental unit of life was gaining traction.
  • The book reflects the significant advancements in biology and microscopy that were taking place in the late 19th and early 20th centuries.
  • Scientific discoveries like the conservation of energy and the correlation of forces were deeply influencing biological thought.


  1. The living body is a machine that transforms energy. This is because it follows the law of the conservation of energy, neither creating nor destroying energy but simply converting it from one form to another.
  2. All living things are composed of cells. These are the fundamental units of life, and their activity constitutes the life of the organism.
  3. Cells reproduce by division. They divide into two daughter cells, each containing half of the original cell’s chromatin material.
  4. The nucleus plays a key role in reproduction and heredity. It contains chromosomes, which are responsible for transmitting hereditary traits from parents to offspring.
  5. Protoplasm is the substance of life. However, its complex structure and activity suggest it is a machine rather than a simple chemical compound.
  6. The cell is a complex machine with specialized parts. These parts, including protoplasm, nucleus, and centrosome, work together to carry out vital functions.
  7. There are two types of variations. Congenital variations are inherited from the parents, while acquired variations are developed during the individual’s lifetime.
  8. Natural selection is a key force in evolution. Organisms with traits that make them better adapted to their environment are more likely to survive and reproduce.
  9. Migration and isolation play a role in evolution. By separating populations, these factors can lead to the fixation of new traits.
  10. The direct influence of the environment affects organisms. Changes in environment can lead to variations in organisms, such as changes in skin color or the size of muscles due to use.
  11. Consciousness has a significant impact on evolution. It can lead to social behaviors and adaptations that influence the selection of certain traits.
  12. The history of life can be traced through fossils. These provide evidence of the gradual changes in organisms over millions of years.
  13. Embryological development often mirrors evolutionary history. This parallelism provides insights into the relationships between different organisms.
  14. Comparative anatomy reveals homologies between different species. These similarities indicate shared ancestry and common evolutionary origins.
  15. The process of fertilization involves the union of two reproductive cells. The egg and the sperm each contribute half of the chromosomes to the offspring, ensuring that genetic material from both parents is inherited.
  16. The germ plasm is the hereditary material passed down from generation to generation. It is stored in the reproductive cells and carries the genetic blueprint for the organism.
  17. The inheritance of acquired characters is a controversial topic. While there is evidence that some acquired traits may be inherited, the extent to which this occurs is still debated.
  18. The living organism is a complex hierarchy of machines. The body as a whole is a machine, made up of organs that are themselves machines, which in turn are composed of cells that are also machines.
  19. The origin of life remains a fundamental scientific question. While the evolution of complex organisms from simpler ones is relatively well understood, the creation of the first living cell is still a mystery.
  20. The cell is the simplest known form of life. It is a highly complex machine with remarkable capabilities, and its origin is still a major area of scientific inquiry.


  1. 1/15th of the energy in coal is converted into motive power in a steam engine. This highlights the inefficiency of man-made machines compared to the body’s energy conversion.
  2. A single unicellular organism can produce 16 million offspring in 24 hours. This demonstrates the remarkable reproductive capacity of living organisms.
  3. An elephant, if allowed to breed unhindered for 750 years, could produce 19 million offspring. This illustrates the exponential nature of reproduction and its impact on population growth.
  4. The number of chromosomes in the cells of a species is constant. For example, the ox has 16 chromosomes, while the lily has 24.
  5. The chromosomes in the fertilized egg are derived from both parents. This shows how genetic material is inherited from both mother and father.


  1. Protoplasm: The substance of life, found in all living cells.
  2. Nucleus: The central organ of the cell, containing chromosomes.
  3. Chromosomes: Thread-like structures in the nucleus that carry genetic information.
  4. Centrosome: A small organelle involved in cell division.
  5. Cell division: The process by which a cell replicates, resulting in two daughter cells.
  6. Evolution: The gradual process of change in organisms over time.
  7. Natural selection: The process by which organisms with traits that make them better adapted to their environment are more likely to survive and reproduce.
  8. Heredity: The transmission of traits from parents to offspring.
  9. Variation: Differences in traits between organisms within a species.
  10. Homology: Similarities in the structure of organisms that indicate shared ancestry.


  1. The steam engine: Conn uses the steam engine as a model to illustrate the mechanical nature of the body’s functions. He compares the burning of fuel in the engine to the oxidation of food in the body, and the engine’s mechanism to the body’s complex systems for energy conversion.
  2. The cell: Conn uses the cell as a prime example of a complex machine within the body, highlighting its specialized parts and their roles in vital processes.
  3. The fertilized egg: The fertilization of the egg is used to illustrate the mechanics of heredity, showing how genetic material from both parents is combined to form the offspring.
  4. The horse’s toes: Conn uses the evolution of the horse, with its gradual reduction of toes, as evidence for the influence of use and disuse on the development of organisms.
  5. The antelope and the lion: This example shows how consciousness can indirectly influence the selection of traits. The antelope’s consciousness of danger leads to the development of running speed as a survival adaptation.
  6. The blacksmith’s arm: This example demonstrates the effect of use on the size and strength of muscles.
  7. Migration and isolation: Conn uses the example of a population of organisms with a specific trait migrating to a new area to explain how these factors can lead to the fixation of new traits.
  8. The printing press: This analogy highlights the importance of heredity in preserving variations and allowing for progress in evolution. Just as printing allows for the transmission of knowledge from generation to generation, heredity ensures the transmission of traits.
  9. The city: The concept of a city is used to illustrate the organization of cells in multicellular organisms. Conn compares the various functions of the city to the specialized roles of cells in the body.
  10. The hunter and the metropolis: This example clarifies the difference between individual cells and the organization of cells in a multicellular organism. Conn argues that the egg contains the potential for the full organism, just as a single hunter does not contain the entirety of a metropolis within himself.


The Story of the Living Machine offers a groundbreaking perspective on the living organism as a complex, intricate machine. Conn masterfully weaves together the principles of evolution, the conservation of energy, and the intricate workings of the cell to present a compelling picture of life.

While acknowledging the limitations of our understanding, Conn emphasizes the remarkable progress made in biology, particularly in the understanding of the cell and its role in reproduction and heredity. He also underscores the enduring mystery surrounding the origin of life and the challenges of explaining the fundamental properties of the living machine. This book serves as a testament to the enduring quest to understand the nature of life through the lens of scientific inquiry.

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