Sunday, May 09, 2021

Friday, May 07, 2021

Kidneys Revisited

Some ten years ago I engaged in a sparring match on the question of כליות יועצות, Chazal's statement that the kelayos, apparently the kidneys, give counsel. My sparring partner, Rabbi Dr. Natan Slifkin, asserted that Chazal believed that thought takes place in the kidneys, not in the brain. I argued that this was a metaphor, as the two kidneys incline towards each other as if counseling one another. There were several post on both his and my blog going back and forth. See, for example,

One can also follow the search at

and look at the top results.

But, I recently learned Berachos 61a again:

ת"ר שתי כליות יש בו באדם אחת יועצתו לטובה ואחת יועצתו לרעה ומסתברא דטובה לימינו ורעה לשמאלו דכתיב (קהלת י, ב) לב חכם לימינו ולב כסיל לשמאלו

...תנו רבנן כליות יועצות לב מבין לשון מחתך פה גומר

and a new thought struck me.

I would like to suggest that kelayos are the term that Chazal used to refer to the two hemispheres of the brain. The term is a borrowed term, as the primary reference is to the kidney (first illustration), and only used by extension for the cerebral hemisphere (second illustration). Yet the sacrificial offerings of the kidneys may in turn be seen as symbolic of the two halves of the brain.

As of yet, I have no independent evidence for this hypothesis, but I wanted to put it out there and perhaps someone will find such evidence.


1. "Erasistratus described four ventricles in the brain, noting that the fourth ventricle under the cerebellum communicated with the third, whereas Herophilus seems not to have noticed the third ventricle: this may have been the first description of the cerebral aqueduct (Tsuchiya et al. 2015). He likened the cerebral gyri to the coils of the small intestine and, long before Thomas Willis (1664), he suggested that the extensive cortical surface of the human brain was in some way related to intelligence, …"

2.  "According to the theory of TCM [Traditional Chinses Medicine], the brain is an outgrowth of and is nourished by the kidney. Brain defects and deterioration of the brain may be prevented, limited, or halted by the ingestion of kidney tonics. And, the energy from the kidney, that is called kidney essence, can produce marrow including cerebral marrow, spinal cord, and bone marrow. As Huangdi's Classics on Medicine said: “the brain is sea of marrow” and “kidney stores essence to generate marrow” [15]. The cerebral marrow can nourish the brain and maintain the physiological functions of the brain. If the kidney essence is insufficient, the production of cerebral marrow will be reduced, leading to various symptoms, such as dizziness, amnesia, and retard response.

3. Both the brain and the kidney have a cortex and a medulla.

Monday, May 03, 2021

My 8th Siyum on Talmud Bavli, 20 Iyar 5781

Major hakoras ha'tov to the Hanhalah and eighth grade talmidim  at YBH for making the siyum such a memorable occasion. May we continue to be mechazek each other!

Sunday, May 02, 2021

Rav Dessler on Hitting Children

Rav Dessler's letter on hitting children.
Michtav Me'Eliyahu vol. 3 pp. 360-362.
An English translation in two parts is at:

Mavo HaTalmud part 1

After a three part series on Klalei Horo'oh - How We Rule in Disputes of Tannaim and Amoraim, we are now going to beginning of the Mavo HaTalmud and starting with the

Basic principles from the Mavo HaTalmud of Rabbi Shmuel HaNaggid with the Kitzur Klallim and other commentaries.

The Mavo is printed in the back of the Vilna Bavli Berachos and can also be found at

Information on Rabbi Shmuel HaNaggid can be found at: