Chullin 60b ~ The Great Tu-Bishvat Eclipse of 2019

Tonight is the 15th day of the Hebrew month of Shevat - better known as Tu-Bishvat. It is the day which traditionally marks “the new year for trees” and on which many of us will make a Tu-Bishvat seder (kind of like a Passover Seder, but without all the cleaning). As a special treat, there will also be a total lunar eclipse tonight, which will be visible from North and South America, Europe and Israel. In the following passage of Talmud that we will learn at the end of this week, there is a wonderful reminder to ponder the relationship of the sizes of the sun and the moon:

חולין ס, ב

רבי שמעון בן פזי רמי כתיב (בראשית א, טז) ויעש אלהים את שני המאורות הגדולים וכתיב את המאור הגדול ואת המאור הקטן אמרה ירח לפני הקב"ה רבש"ע אפשר לשני מלכים שישתמשו בכתר אחד אמר לה לכי ומעטי את עצמך 

אמרה לפניו רבש"ע הואיל ואמרתי לפניך דבר הגון אמעיט את עצמי אמר לה לכי ומשול ביום ובלילה אמרה ליה מאי רבותיה דשרגא בטיהרא מאי אהני אמר לה זיל לימנו בך ישראל ימים ושנים אמרה ליה יומא נמי אי אפשר דלא מנו ביה תקופותא דכתיב (בראשית א, יד) והיו לאותות ולמועדים ולימים ושנים זיל ליקרו צדיקי בשמיך (עמוס ז, ב) יעקב הקטן שמואל הקטן (שמואל א יז, יד) דוד הקטן 

חזייה דלא קא מיתבא דעתה אמר הקב"ה הביאו כפרה עלי שמיעטתי את הירח והיינו דאמר ר"ש בן לקיש מה נשתנה שעיר של ראש חדש שנאמר בו (במדבר כח, יא) לה' אמר הקב"ה שעיר זה יהא כפרה על שמיעטתי את הירח 

Rabbi Shimon ben Pazi explains: When God first created the sun and the moon, they were equally bright. Then, the moon said before the Holy One, Blessed be He: Master of the Universe, is it possible for two kings to serve with one crown? One of us must be subservient to the other. God therefore said to her, i.e., the moon: If so, go and diminish yourself.

She said before Him: Master of the Universe, since I said a correct observation before You, must I diminish myself? God said to her: As compensation, go and rule both during the day along with the sun and during the night. She said to Him: What is the greatness of shining alongside the sun? What use is a candle in the middle of the day? God said to her: Go; let the Jewish people count the days and years with you, and this will be your greatness. She said to Him: But the Jewish people will count with the sun as well, as it is impossible that they will not count seasons with it, as it is written: “And let them be for signs, and for seasons, and for days and years” (Genesis 1:14)….

God saw that the moon was not comforted. The Holy One, Blessed be He, said: Bring atonement for me, since I diminished the moon.The Gemara notes: And this is what Rabbi Shimon ben Lakish says: What is different about the goat offering of the New Moon, that it is stated with regard to it: “For the Lord” (Numbers 28:15)? The Holy One, Blessed be He, said: This goat shall be an atonement for Me for having diminished the size of the moon.

God needs a monthly sacrifice because he diminished the size of the moon! Wow. That’s a theological statement that needs some unpacking. But let’s stay focussed and turn our attention to…

Why we see a lunar eclipse

Here is what will happen on the Tu-Bishvat Eclipse of Sunday night/Monday morning

A lunar eclipse occurs when the earth lies between the sun and the moon. The shadow of the earth then covers the moon, and we see a lunar eclipse. As NASA helpfully explains, during some stages of the lunar eclipse, the Moon will appear reddish. This is because the only remaining sunlight reaching the Moon at that point is from around the edges of the Earth, as seen from the Moon's surface.

When to see the eclipse

On the east coast of the US, the eclipse will begin at 9.36pm on Sunday night and reaches a maximum at 12.12am. On the west coast things will be earlier - you will see the total eclipse starting at 9.12pm. But if you live in London England, you ‘ll have to step outdoors at the ungodly hour of 4.41am on Monday morning to witness the earth cast its shadow on the moon.

What to look for in Jerusalem

In Jerusalem you will be able to see a near total lunar eclipse - (the moon will be 97% covered by the shadow of the earth) at 6:38am on Monday morning. However, this true maximum point of this eclipse cannot be easily seen in Jerusalem because the Moon is below the horizon at that time. To get a better view you will have to head to high point or find an unobstructed area with free sight to the west-northwest for the best view of the eclipse. But be quick. The moon will set barely three minutes later, at 6:41am, and the combination of a very low moon and the total eclipse phase makes the Moon so dim before it sets, that it might disappear from view some time before it sets.

We have discussed how the Talmud understands lunar and solar eclipses several times (like here and here and here). How lucky we are that the moon was commanded to diminish itself and banished to the night sky (mostly). So set your alarms, look to the skies, and pray for a cloudless night.

Chullin 47b ~ Red Babies, Green Babies, and other Neonatal Colors

חולין מז, ב

רבי נתן אומר פעם אחת הלכתי לכרכי הים באתה אשה אחת לפני שמלה בנה ראשון ומת שני ומת שלישי הביאתו לפני ראיתיו שהיה אדום אמרתי לה בתי המתיני לו עד שיבלע בו דמו המתינה לו ומלה אותו וחיה והיו קורין אותו נתן הבבלי על שמי

ושוב פעם אחת הלכתי למדינת קפוטקיא באתה אשה לפני שמלה בנה ראשון ומת שני ומת שלישי הביאתו לפני ראיתיו שהיה ירוק הצצתי בו ולא היה בו דם ברית אמרתי לה בתי המתיני לו עד שיפול בו דמו המתינה לו ומלה אותו וחיה והיו קורין אותו נתן הבבלי על שמי

 Rabbi Natan says: Once I went to the cities overseas, where one woman came before me who circumcised her first son and he died, and she circumcised her second son and he died, and out of concern that circumcising her third son might cause him to die as well, she brought him before me. I saw that he was red, so I said to her: My daughter, wait for him until his blood is absorbed into him. She waited for him until his blood was absorbed into him and then circumcised him, and he survived. And they would call him Natan the Babylonian after my name. 

Rabbi Natan further related: And on another occasion I went to the state of Cappadocia, and a woman came before me who circumcised her first son and he died, and she circumcised her second son and he died. Out of concern that circumcising her thirds on might cause him to die as well, she brought him before me. I saw that he was green. I looked at him and saw that he did not have the blood of circumcision in him, [i.e., he had a deficiency of blood such that no blood would emerge from the circumcision]. I said to her: My daughter, wait until his blood enters him. She waited for his blood to increase and then circumcised him, and he survived. And they would call his name Natan the Babylonian after my name.

Hemophilia A

We have had several occasions in the past to review cases similar of baby boys and the dangers of circumcision, most recently when we studied Chullin 4a and its relation to Hemophilia A. But this is the first time there is a discussion of skin color. Rabbi Natan describes a red looking baby boy and a green looking baby boy. Since in each case there were siblings who had died under similar conditions, it is reasonable to assume that these cases too were caused by hemophilia A. Rabbi Natan’s babies survived because they did not have two copies of the gene for hemophilia. Instead they carried only one copy of the gene which is the cause of this disease. It is a mutation in the F8 gene,which controls the manufacture of Factor VIII, a key component of the clotting cycle. You can see this in the diagram (showing a normal father and carrier mother.) Only half the boys will (on average) become hemophiliacs.

However, there are alternative suggestions, which do not ascribe these colors to hemophilia alone. Let’s start with…

The Red baby boy

In his classic work התלמוד וחכמת הרפואה -The Talmud and Medicine (Berlin 1928, p231-2), I.L Katzenelsohn claimed that the red baby disease is erythema neonatorum. His family also carried hemophilia (because his two brothers had bled to death after their circumcisions), but this third baby was also red. Erythema (toxicum) neonatorum is a common finding in newborns and is thought to be due to an immune reaction (though to what remains unknown). It is a benign condition, and needs no treatment. Rabbi Natan believes that a presumption of hemophilia can only be made once it has been seen three times. This had not yet happened (two previous brothers had died, not three) and so he ordered that the brit can go ahead once the redness cleared up. Luckily, the boy was only a carrier of hemophilia (he was heterozygous for the F8 gene), and so he survived the circumcision.

Others are not so sure what this redness indicated. “I have no idea to what the rabbis are referring to" wrote Dr. Abraham Abraham (that’s his real name, not a typo,) in his work on medical halacha נשמת אברהם, The Soul of Avraham (יורה דעה 263:3). He was a Professor of Medicine at Hebrew University and Hadassah Medical School, so if he is stumped I guess we all are. So now let’s turn to…

The Green Baby Boy

This one is really hard to figure out, because there isn’t agreement on precisely what is meant by the description that the baby is ירוק, green. Rashi describes it as “the color of grass” which is - at least in the summer - a nice green color. Tosafot, being Toasafot, disagrees, and suggests that it is a sky blue color. And even more colors appear in later halachic works.

Katzenelsohn believed the “green” color is more of a yellow one, which is common in neonatal jaundice. (“Where is the best place to detect neonatal jaundice?” I was asked as a medical student. “Um, the sclera?” I offered in reply. “Nope said the doctor, happily pimping me, “in the parking lot, - where the sun provides the best illumination.” But I digress). Neonatal jaundice is an almost universal finding in newborns, and results from a breakdown of the fetal hemoglobin that is no-longer needed now that the baby is ex-utero. Julius Preuss (Biblical-Talmudic Medicine, Jason Aronson 1978 p167) believes the green color does not mean green, but instead it means pale. In this reading the baby was anemic, meaning that it lacked hemoglobin.

And what would the green-is-really blue suggestion of Tosafot indicate? Well, blue skin is called cyanosis, and results from too-little oxygen reaching the tissues. The feet and toes of newborns are often blue for a couple of days, as they develop their own oxygen carrying capacity (having spent nine happy months relying on mom’s). Some of the things that cause peripheral cyanosis include the cold (that’s when your arteries no-longer want to shunt warm blood to your freezing fingers), heart failure (the heart is too tired to pump oxygenated blood to the peripheries) or chronic lung disease (the lungs just can’t get enough oxygen through them and into the bloodstream). Central cyanosis is usually much more serious. It can be caused by infections like pneumonia (and did I mention that it was a defining feature of impending death during the Great Influenza Pandemic of 1918?) In the context of a newborn, it may indicate congenital heart disease. Some forms of congenital heart disease are fatal, but today there are a number of operations (or sometimes several) that can save the neonate’s life.

The Overarching Principle of Brit Milah

Whatever the color of the little baby boy or the number of brothers who may have died as a result of circumcision, Jewish law has evolved from these descriptions in the Talmud to a position that is clear and absolute.

שולחן ערוך יורה דעה רס’ג, א

באלו הדברים שאין מלין ולד שיש בו חשש חולי דסכנת נפשות דוחה את הכל שאפשר לו למול לאחר זמן ואי אפשר להחזיר נפש אחת מישראל לעולם

In all of these conditions in which we do not circumcise the baby because of the risk of a fatal outcome, the circumcision is postponed to a later date [when the child is now healthy]. For it is possible to postpone the day of circumcision, but it is impossible ever to replace the soul of a Jewish baby.

Chullin 42a ~ Halachic Reality and Anatomic Reality: the Case of the Treif Animal

With the start of the third chapter of Chullin we take a deep dive into animal anatomy.

אלו טרפות בבהמה נקובת הוושט ופסוקת הגרגרת ניקב קרום של מוח ניקב הלב לבית חללו נשברה השדרה ונפסק החוט שלה ניטל הכבד ולא נשתייר הימנו כלום הריאה שניקבה או שחסרה ר"ש אומר עד שתינקב לבית הסמפונות ניקבה הקבה ניקבה המרה ניקבו הדקין הכרס הפנימית שניקבה או שנקרע רוב החיצונה רבי יהודה אומר הגדולה טפח והקטנה ברובה המסס ובית הכוסות שניקבו לחוץ נפלה מן הגג נשתברו רוב צלעותיה ודרוסת הזאב רבי יהודה אומר דרוסת הזאב בדקה ודרוסת ארי בגסה דרוסת הנץ בעוף הדק ודרוסת הגס בעוף הגס זה הכלל כל שאין כמוה חיה טרפה

These wounds constitute tereifot in an animal,rendering them prohibited for consumption:

1. A perforated esophagus, where the perforation goes through the wall , 

2. or a cut trachea.

3. If the membrane of the brain was perforated, 

4. or if the heart was perforated to its chamber; 

5. if the spinal column was broken and its cord was cut; 

6. if the liver was removed and nothing remained of it…

7. a lung that was perforated

8. or a lung missing a piece….

9. If the abomasum was perforated

10. or the gallbladder was perforated, 

11. or the small intestines were perforated, it is a tereifa…

This is the principle: Any animal that was injured such that an animal in a similar condition could not live for an extended period is a treifa, the consumption of which is forbidden by Torah law. 

The original meaning of the term treif in the Torah is torn, and it describes a domestic animal that was attacked by a wild animal and suffered an injury that led to its death.

“וְאַנְשֵׁי־קֹ֖דֶשׁ תִּהְי֣וּן לִ֑י וּבָשָׂ֨ר בַּשָּׂדֶ֤ה טְרֵפָה֙ לֹ֣א תֹאכֵ֔לוּ לַכֶּ֖לֶב תַּשְׁלִכ֥וּן אֹתֽוֹ׃
You will be holy people to Me: you must not eat flesh torn by beasts in the field; you shall cast it to the dogs.”

— Exodus 22:30

But the rabbis of the Talmud greatly expanded this category - hence the list in the Mishnah that we are studying today. Later in Chullin (57b) there is a dispute as to the prognosis of living animal were it to be declared treif. According to Rav Hunna, if an animal is treif, by definition it cannot live for longer than a year (אמר רב הונא סימן לטרפה י"ב חדש). But there are other opinions (this is, after all, the Talmud): the great editor of the Mishnah, Rabbi Yehudah HaNassi opinion that a treifa is destined to die within 30 days, while a berasia states that a treif animal cannot give birth (leaving open the question about male animals).

““Jason Marcus, chef and owner of the new Traif restaurant on S. Fourth Street in Williamsburg, says the name is just cheeky, not a slap at his mostly Kosher eaters.”

“But [the name] really represents our philosophical view of how restaurants should be free of rules. We’re just people who live for good food.””

It is generally agreed upon that list in today’s Mishnah details the kinds of lesions that would be fatal within a year. And that’s when the problems begin. Some of them are certainly likely to be fatal. For example a perforated esophagus (נקובת הוושט) leads to mediastinitis, an inflammation of the chest cavity. And that is commonly fatal. If the animal swallows something sharp it can pierce not only the esophagus, but the membranes that surround the heart, called the pericardium. Way back in 1955 - at the start of the era of antibiotics - The Australian Veterinary Journal published a case series of twenty-one dairy cows that developed traumatic pericarditis. “Fifteen cases were treated with sulphonamide [an antibiotic] and six were not. ” The six animals untreated cows all died, and even among the cows treated with antibiotics, almost half died. So yes, some lesions recorded in the Mishanh (and later refined in the talmudic discussion which follows) are indeed fatal.

The Case of Serachot

But other lesions that render an animal treif are certainly not fatal. Take for example lung adhesions, called סרחות (serachot, or sircha in the singular), which are discussed in detail later (46b et. seq). These adhesions are fibrous tissues that may run between different lung lobes, or between the lungs and the rib cage. They are common and are caused by a number of conditions, including trauma or previous infections. Many kinds of serichot render an animal treif. But lung adhesions are certainly not lethal. Animals and humans live quite happily with them. In fact this doctor recently told me that the presence of lung adhesions does not prevent lungs from being donated and used for a lung transplant. Now, if they are used in that delicate situation, they most certainly do not have a fatal defect, or anything even close.

the case of the missing liver (and the missing heart)

Opening paragraph of the famous responsa on “the chicken that had no heart”. From שו׳ת חכם צבי, Amsterdam 1712.

Equally puzzling to the modern reader is the sixth category in the Mishna’s list: ניטל הכבד ולא נשתייר הימנו כלום - if the slaughtered animal was found to have no liver. Here’s the thing: an animal cannot live without a liver. If a healthy looking cow - or indeed any cow -was well enough to be slaughtered, it must have had a liver. So this is not an example of a treif animal - it’s an example of one that could not possibly have existed. But don’t take my word for it.

In 1709 the great rabbi of Hamburg, Zevi Ashkenazi, (better known as the Chacham Zevi, after the name of his responsa) was asked the following question. A young woman had opened a slaughtered chicken to remove the unwanted entrails, while her cat sat at her feet “waiting patiently for anything that may fall to the ground.” To her great surprise, the young woman found that the chicken did not have a heart, and so assumed the bird was treif. Not so, claimed her mother, who apparently owned the chicken. The cat must have eaten it, when it was thrown to the ground together with the entrails. The young women was however quite adamant, and insisted she had never fed anything that resembled a heart to the cat. The bird had been perfectly healthy before it was slaughtered, eating and drinking like any other healthy chicken, (וגם בעודנה בחיים חיותה היתה חזקה ובריאה ובכל כחה לאכול ולשתות). The question of the kashrut of the bird was brought to the local rabbis, who declared it to be treif, on the basis that while alive, it had no heart.

The Chacham Zevi was asked to weigh in on the matter. “It is absolutely clear to any person who has a wise heart” he wrote, apparently enjoying the play on words, “or who has a brain in his skull, that it is impossible for any creature to live for even a moment without a heart…Clearly, the heart fell out when the bird was opened, and that cat ate it…It is obvious that the chicken is permitted” Strike one for common sense. You would think. But not so fast. This answer of the Chacham Zevi engendered one of the great halachic disputes of the eighteenth century. In one corner, the Chacham, and in the other at least four leading rabbinic figures who vehemently opposed this ruling: Naphtali Katz of Frankfurt, Moses Rothenburg, David Oppenheim (who was the Chief Rabbi of Prague, no less) and Jonathan Eyebeschuetz (who spent much of his later life fighting halachic battles against Rabbi Yaakov Emden, who was the son of the Chacham Zevi). It got nasty, but that’s a story for another day.

Halachic Reality

No bird or animal can live without a heart, and none can do so without a liver. So there can be no case, like the one in the Mishnah, in which a healthy living animal was slaughtered and found to be without a liver.

Some of the categories of treifot overlap with conditions that are indeed incompatible with life. Others are perfectly innocuous and compatible with a long and healthy life. And a few make no sense given what we know about animal physiology. But none should be thought of as describing an anatomical reality. They describe instead a halachic reality, a reality that reflected a world some 1,500 years ago. And while our understanding of physiology has changed, these halachic classes remain a fixed part of Jewish tradition. Here is the great Maimonides, who was obviously troubled by the chasm that sometimes exists between halacha and facts.

רמב’ם משנה תורה הלכות שחיטה י, יג וְכֵן אֵלּוּ שֶׁמָּנוּ וְאָמְרוּ שֶׁהֵן טְרֵפָה אַף עַל פִּי שֶׁיֵּרָאֶה בְּדַרְכֵי הָרְפוּאָה שֶׁבְּיָדֵינוּ שֶׁמִּקְצָתָן אֵינָן מְמִיתִין וְאֶפְשָׁר שֶׁתִּחְיֶה מֵהֶן אֵין לְךָ אֶלָּא מַה שֶּׁמָּנוּ חֲכָמִים שֶׁנֶּאֱמַר (דברים יז יא)"עַל פִּי הַתּוֹרָה אֲשֶׁר יוֹרוּךָ

Each one of these lesions that were declared treif remain so even if modern medicine can demonstrate that some of them are not actually fatal, and that it is indeed possible to live despite them. Rather we must follow these rabbinic categories, as the Torah states“ You shall act in accordance with the instructions given you and the ruling handed down to you; [you must not deviate from the verdict that they announce to you either to the right or to the left.]

In more recent times, Rabbi Avrohom Yeshaya Karelitz, better known as the Chazon Ish, also addressed this question. “We see today” he wrote, “that very often surgeons operate on the abdomen of a person [with an injury like one found in a treif animal], and he is completely cured, and lives a long life.” But this does nothing to change the way we view the categories of treif . These depend solely on what was decided by the rabbis of the Talmud, and no modern findings can change them.

But what happens when science suggests that the act of shechita inflicts unnecessary pain on the animal? That’s coming up, on Talmudology.

Chullin 22b ~ Yellow Pigeons, Folk Medicine and Hepatitis

It was while working as a physician in Jerusalem in the 1990s that I first heard of a bizarre remedy to treat jaundice. A pigeon is placed on the belly of the yellow patient. After a few minutes, the jaundice is drawn out of the patient and enters the bird, which promptly dies. I never got to see the miracle in person, but people swore by it. I was reminded of this folk remedy by a passage in today’s page of Talmud, about which more below.

Pigeons for jaundice, Really?

At this point, a few of you are nodding and saying “sure, I’ve heard of that.” One or two of you might be saying “hey, I’ve seen that work/not work with my own eyes.” But most of you will be saying “what on earth is this all about?” So before we go on, let’s talk about the myth of using pigeons to cure jaundice.

We will never know how, where or when the myth began. It is mentioned in a book called Ta’ami Haminhagim טעמי המנהגים (Reasons for the Customs) by Abraham Isaac Sperling, first published in Poland in 1896. It is still in print today. At the back of the book is a small section called “Remedies” ( סגולות) where you will read this gem (based, apparently on this source):

אברהם יצחק שפרלינג טעמי המנהגים, ירושלים הוצאת אשכול 1957

“A remedy for yellowness:
Take a male pigeon for a man and a female pigeon for a woman. Place it on the umbilicus, and the pigeon will draw out all of the yellowness until there is none left, and the pigeon dies. This has been tested (בדוק).”

— אברהם יצחק שפרלינג טעמי המנהגים, ירושלים הוצאת אשכול 1957

APPARENTLY It’s not just PIGEONS

In 1801 Frances Barrett (“Professor of chemistry, natural and occult Philosophy, the Cabala, &c. &c.”) published The Magus, or Celestial Intelligencer; being a Complete System of Occult Philosophy. The illustrious professor had come across the pigeon-cures-jaundice myth in a slightly different form: it was the duck-cures-colic. “It is expedient for us to know” he helpfully informs us on page 37,“that there are some things which retain virtue only while they are living, others even after death. So in the colic, if a live duck is applied to the belly, it takes away pain, and the duck dies.”

Suffocation and a Ruptured Spleen

People still do this; you can find it discussed at sites like The Yeshiva World, (“A close relative of mine did this procedure for his father and it worked”) Ohr Somayach (“strong hearsay evidence”) and on the Hebrew site Ynet (אני מכיר רופא מכובד ומוכר …לאחר פרק זמן של חודשים הסכים לתת לביתו את הטיפול ביונים הוא עשה זאת ) And in case you want to see it in action, here is a video of the process. Watch through to the end and count how many pigeons were crushed to death by the charlatan performing the procedure. Warning: for anyone with a modicum of sensitivity, it’s hard to watch.

I know what you are thinking. The guy in the white coat simply crushed the pigeons to death. And you are correct. In fact a post mortem on the bodies of some of these poor birds revealed the cause of death as was a ruptured spleen.

A primer on Jaundice

Jaundice is a yellowing of the skin, though it is even more noticeable in the sclera. It is not a disease, but a symptom. Jaundice becomes apparent when when there is a buildup of bilirubin in the blood. Bilirubin is a breakdown product of heme, which is produced when red blood cells are broken down. It is then excreted via the liver.

There are several causes of jaundice, the most common of which is hepatitis (literally, an inflammation of the liver). Hepatitis itself has many different causes. Viral hepatitis is most often caused by hepatitis A - that’s the one you see when people in close contact don’t wash their hands enough. It is a self limiting disease lasting a few days or so. Hepatitis B, C and D are far more serious, and can lead to liver failure and chronic jaundice. Alcohol is another leading cause of hepatitis, and causes cirrhosis of the liver. But not all jaundice is caused by a liver problem. Newborn babies are very often jaundiced. This happens because they are busy breaking down their fetal hemoglobin, releasing heme in the process, which is then turned into bilirubin. Their livers are working just fine.

So now you understand why crushing a pigeon to death on a person with hepatitis A might appear to work. It is because hepatitis A is a self-limiting disease; it goes away after a few days, as does the jaundice. The pigeon had nothing to do with it. You could clap your hands three times and the hepatitis would also go away. The other causes of hepatitis are chronic, and sometimes fatal. In these cases, no amount of chicanery would be associated with a cure, because there wouldn’t be one (unless you have hepatitis C, in which case a new and very expensive drug will actually cure you, no pigeons needed).

Yellow Pigeons in today’s Daf

In today’s page of Talmud there is a discussion about sacrificing pigeons and doves. And the color yellow features prominently:

חולין כב, ב

ת"ר יכול יהו כל התורים וכל בני היונה כשרים תלמוד לומר מן התורים ולא כל התורים מן בני היונה ולא כל בני יונה פרט לתחילת הציהוב שבזה ושבזה שפסול מאימתי התורים כשרים משיזהיבו מאימתי בני יונה פסולין משיצהיבו

The Sages taught in a baraita: I might have thought all  old doves or all young pigeons would be fit for sacrifice; therefore, the verse states: “Of doves,” and not all doves; “of young pigeons,” and not all young pigeons.This serves to exclude birds at the beginning of the yellowing of their neck plumage, which is a marker of both doves and pigeons. They are unfit as doves because they are not sufficiently old and as pigeons because they are no longer young. The tanna elaborates: From when are the doves fit? It is from when the color of their feathers turns a glistening gold. From when are the pigeons unfit? It is from when their feathers turn yellow.

The Sages here describe how the color of both doves and pigeons changes from or to a yellow. (But I have not been able to find a description of this actually happening in any of the ornithology texts I consulted. )

Transference

So now we can understand why these birds were associated with jaundice - because they were once described as changing from being yellow or becoming yellow themselves. By the act of transference, the pigeons were able to draw out the jaundice. There are many examples of transference in Judaism, where an animal symbolically absorbs and removes sin. There was the Temple ritual in Jerusalem, in which the owner lay his hands on the head of the animal brought as a sacrifice to expiated for sin. There is the ritual of Tashlich on Rosh Hashanah, in which our sins are symbolically cast away as we throw bread into a stream. And there is the controversial ritual of Kaparrot, in which a chicken (or, more kindly, money) is swung over the head while reciting “this is my exchange, this is my substitute, this is my atonement. This rooster will go to its death, while I will enter and proceed to a good long life and to peace.” It doesn’t end well for the chicken, but at least it is slaughtered for food and given to the poor. If only those pigeons had it so lucky.