In 1881, doctor William Halsted rushed to help his sister Minnie, who was hemorrhaging after childbirth.

1881年，William Halsted 醫生趕去幫他姊姊 Minnie 的忙，她因為生產而大出血。

He quickly inserted a needle into his arm, withdrew his own blood, and transferred it to her.

他快速地在自己手臂插上針、抽出血，然後把血輸給 Minnie。

After a few uncertain minutes, she began to recover.

過了不知道幾分鐘，她慢慢好多了。

Halsted didn't know how lucky they'd gotten.

Halsted 不知道他們有多幸運。

His transfusion only worked because he and his sister happened to have the same blood type—something that isn't guaranteed, even among close relatives.

他的輸血會成功，完全是因為他和姊姊剛好同血型，即使是親近的親戚也不一定會是同個血型。

Blood types hadn't been discovered by Halsted's time, though people had been experimenting with transfusions for centuries—mostly unsuccessfully.

雖然人們已經做輸血實驗好幾個世紀了 (大多都不成功)，但在 Halsted 的時代，血型還沒被發現。

In 1667, a French physician named Jean-Baptiste Denis became the first to try the technique on a human.

1677年，法國醫生 Jean-Baptiste Denis 成為首位在人身上輸血的人。

Denis transfused sheep's blood into Antoine Mauroy, a man likely suffering from psychosis, in the hopes that it would reduce his symptoms.

Denis 把綿羊的血輸給 Antoine Mauroy，Antoine 因為精神疾病而遭受巨大痛苦，Denis 希望輸血會減少症狀。

Afterward, Mauroy was in good spirits.

輸血後，Mauroy 精神極好。

But after a second transfusion, he developed a fever, severe pain in his lower back, intense burning in his arm, and he urinated a thick, black liquid.

不過在第二次輸血後，Mauroy 發燒、背部低處產生劇痛、手臂有灼燒感，而他之後小便時，排出了厚重的黑色液體。

Though nobody knew it at the time, these were the signs of a dangerous immune response unfolding inside his body.

雖然當時沒人知道，但這些是他身體產生危險的免疫反應的徵狀。

This immune response starts with the production of proteins called antibodies, which distinguish the body's own cells from intruders.

免疫反應開始於蛋白質的製造，製造出抗體，而抗體可以分辨自身的細胞和侵入的細胞。

They do so by recognizing the foreign proteins, or antigens, embedded in an intruder's cell membrane.

他們會辨認外來的蛋白質，或是附著在入侵細胞薄膜上的抗原。

Antibodies latch onto the antigens, signaling other immune cells to attack and destroy the foreign cells.

抗體會附在抗原身上，指示其他免疫細胞攻擊、摧毀外來細胞。

The destroyed cells are flushed from the body in urine.

被摧毀的細胞，會隨著尿液被排出體外。

In extreme cases, the massive breakdown of cells causes clots in the bloodstream that disrupt the flow of blood to vital organs, overload the kidneys, and cause organ failure.

在極端案例裡，細胞的大量毀壞，可能造成血塊凝聚，進而堵住流向重要器官的血管，讓腎臟過度工作，最後造成器官衰竭。

Fortunately, Denis's patient survived the transfusion.

幸運的是，Denis 的病患安然度過這次輸血。

But, after other cross-species transfusions proved fatal, the procedure was outlawed across Europe, falling out of favor for several centuries.

然而，其他跨物種的輸血被證明是致命的，於是輸血在歐洲被宣告非法，在接下來的好幾個世紀都不受歡迎。

It wasn't until 1901 that Austrian physician Karl Landsteiner discovered the blood types, the crucial step in the success of human to human blood transfusions.

直到1901年，奧地利的醫生 Karl Landsteiner 發現了血型，在人對人輸血的歷程上跨出重大的一步。

He noticed that when different types were mixed together, they formed clots.

他注意到如果把不同血型的血混在一起，會形成血塊。

This happens when antibodies latch on to cells with foreign antigens, causing blood cells to clump together.

這是因為當抗體和外來抗原要附在細胞上時，血球會凝聚在一塊。

But if the donor cells are the same blood type as the recipient's cells, the donor cells won't be flagged for destruction, and won't form clumps.

但如果供體細胞和接受者的細胞是同種血型，供體細胞不會出現需被摧毀的標誌，也就不會造成血塊。

By 1907, doctors were mixing together small amounts of blood before transfusing it.

到 1907 年時，在輸血前，醫生會先把少量的血混在一起。

If there were no clumps, the types were a match.

如果沒有血塊，血型就是一對。

This enabled them to save thousands of lives, laying the foundation for modern transfusions.

這讓醫生們拯救了上千條生命，為現代輸血建立基礎。

Up to this point, all transfusions had occurred in real time, directly between two individuals.

到現在，所有輸血都是同時於兩個個體間直接進行。

That's because blood begins to clot almost immediately after coming into contact with air—a defense mechanism to prevent excessive blood loss after injury.

因為只要接觸空氣，血液幾乎是立即結塊——這是個防衛機制，防止受傷後血液大量流失。

In 1914, researchers discovered that the chemical sodium citrate stopped blood coagulating by removing the calcium necessary for clot formation.

1914年，學者發現檸檬酸鈉可以阻止血液凝固，因為它會移除凝固過程所需的鈣。

Citrated blood could be stored for later use—the first step in making large scale blood transfusions possible.

含檸檬酸鈉的血可以被儲存、之後再用，這是讓大量輸血成為可能的第一步。

In 1916, a pair of American scientists found an even more effective anticoagulant called heparin, which works by deactivating enzymes that enable clotting.

在1916年，一對美國科學家發現更有效的抗凝血劑——肝磷脂，可以讓凝血的酵素失能。

We still use heparin today.

我們至今仍在使用肝磷脂。

At the same time, American and British researchers developed portable machines that could transport donor blood onto the battlefields of World War I.

與此同時，美國和英國的學者發展出攜帶式機器，在一戰時將血液供體運到戰場上。

Combined with the newly-discovered heparin, medics safely stored and preserved liters of blood, wheeling it directly onto the battlefield to transfuse wounded soldiers.

與新發現的肝磷脂結合，醫療人員安全地儲存、保留了好幾升的血，把血直接運到戰場上，輸血給受傷的士兵。

After the war, this crude portable box would become the inspiration for the modern-day blood bank, a fixture of hospitals around the world.

戰爭過後，這個簡陋的攜帶式箱子，成為現代血庫的發明靈感，全世界醫院都有的配備。

Did you know that horseshoe crab blood plays an essential role in the medical industry?

你知道鱟血在醫療界扮演重要角色嗎？

Find out why we're so dependent on this ancient creature with this video, or continue understanding your circulatory system by learning more about blood types.

想知道我們為何如此依賴這隻古老生物的話，按這支影片，或是透過認識血型，繼續了解循環系統。