Wednesday, April 20, 2005

Acharei Mot #2: דמו בנפשו

In Parshat Acharei Mot, (Vayikra 17:14)

יד כִּי-נֶפֶשׁ כָּל-בָּשָׂר, דָּמוֹ בְנַפְשׁוֹ הוּא, וָאֹמַר לִבְנֵי יִשְׂרָאֵל, דַּם כָּל-בָּשָׂר לֹא תֹאכֵלוּ: כִּי נֶפֶשׁ כָּל-בָּשָׂר דָּמוֹ הִוא, כָּל-אֹכְלָיו יִכָּרֵת. 14 For as to the life of all flesh, the blood thereof is all one with the life thereof; therefore I said unto the children of Israel: Ye shall eat the blood of no manner of flesh; for the life of all flesh is the blood thereof; whosoever eateth it shall be cut off.

A certain prominent physician in my shul pointed out a very interesting Ibn Ezra on this pasuk a few years ago:
דמו בנפשו. הוא דבק עם הנפש כי ידוע שהגידים היוצאים מפאת שמאל הלב מחולקים בחצי לדם ולרוח כדמות שמן זית עם האור
It {blood} is connected with the nefesh {life, here "spirit"}, for it is known that the arteries leaving from the left side of the heart are divided half with blood and spirit {wind} in the manner of olive oil with the flame.

He noted that this commentary by Ibn Ezra seems to recognize a modern medical fact - that there is a dual circulation , one of oxygenated blood (blood carrying oxygen, the oxygen obtained from the lungs) and unoxygenated blood. Further, as we know, the oxygenated blood is pumped out of the left side of the heart, and the unoxygenated blood comes in to the right side of the heart. Ibn Ezra thus seems to know of arteries, which carry oxygenated blood, and veins, carrying unoxygenated blood.

This would be astounding, for Ibn Ezra was born in 1092 and passed on in 1167, and it was only in 1628 that William Harvey suggested the modern model. To cite Encarta:
Only in the past 400 years have scientists recognized that blood moves in a cycle through the heart and body. Before the 17th century, scientists believed that the liver creates new blood, and then the blood passes through the heart to gain warmth and finally is soaked up and consumed in the tissues. In 1628 English physician William Harvey first proposed that blood circulates continuously. Using modern methods of observation and experimentation, Harvey noted that veins have one-way valves that lead blood back to the heart from all parts of the body. He noted that the heart works as a pump, and he estimated correctly that the daily output of fresh blood is more than seven tons. He pointed out the absurdity of the old doctrine, which would require the liver to produce this much fresh blood daily. Harvey’s theory was soon proven correct and became the cornerstone of modern medical science.

He wanted to show from here that Chazal, such as represented by Ibn Ezra, wrote with ruach hakodesh, for how else could Ibn Ezra know that the function of the heart was to pump oxygenated blood from the left hand side, with non-oxygenated blood on the right side?

My first reaction to this is that this is not what Ibn Ezra means. Rather, his description was an attempt to read the pasuk from a contemporary scientific perspective - that is, darshen in a way what was accurate science in his day.

The first hint to this is in Ibn Ezra's use of the phrase כי ידוע, "for it is known." This implies that Ibn Ezra is referring to some well known scientific fact. He is not referring to a drasha of Chazal, for there is no such drasha. He is NOT coming up with this new scientific fact ex nihilo via ruach hakodesh. Further, had no one else known of this fact, the reaction would have been: Huh?

Now, to Harvey proposed that the heart was a pump, but that does not mean that people back then did not know that the blood flowed through the heart, and it does not mean that they did not know a direction of said blood flow, such that the blood flows out the left side.

What of the oxygenated blood coming from the left? I would surmise rather that Ibn Ezra is referring to Greek science, and quite old Greek science at that (pre-Socratic), but which lasted to his day and probably further. I would guess he is actually following Empedocles (see for example here), who proposed his own dual circulation system. He suggested there were two circulations in the body - one of blood, and the other of (fiery) pneuma, an etheal and fiery substance. There were vessels for conveying blood (veins) and vessels for conveying pneuma (arteries = lit. air vessels).

Now we can look again at Ibn Ezra. I would also suggest that the words כדמות שמן זית עם האור are not referring to the connection of oxygen and blood, but rather a description of the pnuema itself.
דמו בנפשו. הוא דבק עם הנפש כי ידוע שהגידים היוצאים מפאת שמאל הלב מחולקים בחצי לדם ולרוח כדמות שמן זית עם האור
It {blood} is connected with the nefesh{life, here "spirit", or pneuma}, for it is known that the arteries leaving from the left side of the heart are divided, half conveying blood and {the other half} for wind {pneuma} which is similar to olive oil in the flame {that is, rareified matter}.
While researching this, I saw another website that make similar claims for the Chinese, but again, I think they are thinking of pneuma and chi, conveyed separately, as opposed to being conveyed by the blood, such that it is not the same.

1 comment:

Otzar Tov said...

He was refering to Erasistratus
check out his wiki page read the part titled medicine


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parshablog is published by (rabbi) josh waxman (joshwaxman [at] yahoo [dot] com), a grad student in Revel, a grad student in a Phd program in computer science at CUNY. i recently received semicha from RIETS. this blog is devoted to parsha as well as whatever it is i am currently learning.