【PEP Edition】Junior Biology Grade 7, Volume 2: From "Intuition" to "Science": The History of Understanding Blood Circulation

Humanity's understanding of blood circulation is a magnificent journey fromnaive philosophical speculationtorigorous experimental science—a great leap that represents not just the accumulation of medical knowledge, but a fundamental shift in the way humans think.

I. The Macro Insight of Eastern Wisdom

Over two thousand years ago, the Chinese medical classic Huangdi Neijing (The Yellow Emperor's Inner Canon) put forth the ideas that "All blood belongs to the heart" and "The meridians flow without ceasing, in a never-ending circular motion". This was a philosophical insight of genius, ahead of its time, which sketched a rudimentary picture of blood flowing in a cycle. However, lacking the support of microscopic dissection and quantitative methods, it remained at an intuitive stage of "knowing the how but not the why."

II. The Blind Spots of Classical Medicine

Galen of ancient Rome believed blood was produced in the liver from food and mixed with the "Vital Spirit" inhaled by the lungs, then "consumed" like fuel in the body's tissues. This linear, consumption-based view dominated medieval medicine for nearly a millennium, leading practitioners to blindly followthe principle of "replenishing what is lacking". For example, they tried to restore strength by having patients drink animal blood, completely overlooking blockages in the circulatory pathways themselves, and were unable to comprehend complex diseases likehypertensionwhich arise from abnormalities in circulatory pressure.

III. The Empirical Leap of Science

The true breakthrough came from the experimental and quantitative methods introduced by Harvey. Through ligation experiments and precise calculations of the heart's pumping volume, he demonstrated that if blood were simply consumed in one direction, the body could never produce such a massive quantity in a short time. This discovery transformed blood from a mystical, magical substance back into a physical medium flowing within a closed system, ushering in the dawn of modern medicine.

QUESTION 1

In the Huangdi Neijing, which statement most directly describes the characteristics of blood flow in the body?

"Replenish what is lacking"

"The meridians flow without ceasing, in a never-ending circular motion"

"The Vital Spirit is inhaled by the lungs"

"Blood is produced by the liver"

QUESTION 2

What was the greatest misconception that Galen's "linear consumption model" introduced to medical treatment at the time?

Believing the heart is a pump

Blindly following the "replenish what is lacking" principle to administer misguided fluid replacement

Discovering capillaries

QUESTION 3

Why was ancient medicine unable to grasp the concept of "hypertension"?

Because the heart had not yet been discovered in ancient times

Because there was a lack of quantitative experimental analysis of pressure and flow rate within a closed system

Because people's blood at that time had no pressure

QUESTION 4

[Short Answer] [Short Answer] [Reading Context: Over two thousand years ago, the classic Chinese medical text Huangdi Neijing already contained statements such as "all blood belongs to the heart" and "the meridians flow without ceasing, in a never-ending circular motion," showing that ancient Chinese people had some understanding of blood circulation. ... Harvey's work pioneered the introduction of experimental methods into physiology, laying the foundation for the development of modern physiology and medicine.] After reading this article, what new insights have you gained about the history of science?

QUESTION 5

From the ceaseless circular flow of the Huangdi Neijing to Galen's Vital Spirit, ancient views of blood were based on intuition. Why was early medicine, lacking experimental evidence, only able to explain phenomena through simple observation? How did this cognitive limitation affect the understanding of concepts like hypertension?