In May 2026 the New York Times Magazine ran a long, beautifully illustrated piece about the interstitium — the fluid-filled spaces that run through and between our tissues. It was careful about the anatomy. Then it walked the reader, step by step, from connective tissue to acupuncture points, from acupuncture points to meridians, and from meridians to a researcher saying the interstitium could be the link between Eastern and Western medicine.
Anyone who works with bodies will feel the pull of that sentence. Which is exactly why it is worth slowing down at each step and asking what the studies underneath it actually show — and, in one case, what the article left out.
The anatomy is real
This part stands. In 2018 a group led by pathologists Neil Theise and Rebecca Wells described fluid-filled spaces supported by bundles of collagen in the wall of the bile duct, then found similar structures in the gut, the bladder, the skin, around arteries and airways, and in fascia. They had been missed for a mundane reason: standard tissue preparation collapses them, so on an ordinary slide they look like tears.
In 2021 the same group tracked tattoo pigment and colloidal silver in surgical samples and followed them from skin and colon into the adjacent fascia, and along the sheaths of nerves and blood vessels that cross from one organ to another. Their conclusion — carefully worded — was that there may be a body-wide network of these spaces. Later work extended the finding to the lungs and the pancreas.
Two things are worth keeping from this. First, the idea is not new, and the researchers say so themselves: a 2023 paper co-written by Wells, Theise and the Padua anatomist Carla Stecco traces it back to Franklin Mall’s dye studies at Johns Hopkins at the turn of the twentieth century. Research on fascia and research on the interstitium genuinely meet — among methodologically serious people. Second, what these studies show is continuity of structure, seen in tissue samples. They do not measure fluid flowing through the living body, and the phrase “a third circulatory system” comes from an interview, not from the papers.
The bridge to acupuncture is interesting — and thin
In 2002 Helene Langevin mapped acupuncture points on serial sections of the arm and found that 80% of them lay on planes of connective tissue between or within muscles. That is a striking number, with one open question the abstract does not answer: connective-tissue planes are everywhere in the arm, so how many randomly chosen points would also have landed on one? Without that baseline, 80% cannot yet be read as more than chance.
The study the article leans on hardest is more recent. In 2021 researchers injected fluorescent dye into the skin of fifteen healthy volunteers, at points on the inner forearm along what is called the pericardium meridian, and at a nearby control spot. Of nineteen injections of fluorescein at the point known as PC6, fifteen — 79% — spread slowly up the arm along a line matching the meridian and resurfaced at another point, PC3. The control injections produced no line. Ultrasound found no blood vessel beneath the path, but did find intermuscular fascia.
The magazine reported that the dye migrated along the meridian in almost all of the volunteers. The study says fifteen of nineteen injections, not people. And it says something else, which the article does not mention at all.
The second dye
The researchers used two dyes. The second, indocyanine green, behaved like the first close to the injection — and then, further up the arm, it spread apart. It did not converge on PC3.
That is the most informative sentence in the paper. If the line were a channel — a meridian with walls — both dyes should have followed it. They did not. The two molecules differ in size and in how strongly they bind to proteins, and they took different routes. The simplest reading is that what the fluorescein showed is how a particular molecule moves through tissue that has a grain: layered, oriented, easier to travel along than across. That is interesting in itself. It is not the same claim as a pathway with its own identity.
We should be clear that this reading is ours; the study does not settle it. But a result that holds for one tracer and not another is exactly the kind of detail that decides what the result means — and exactly the kind that disappears when a finding is retold in one clean line.
The clinical check
There is a second way to test the bridge, and it does not need any dye. If acupuncture worked by acting on specific interstitial routes, then placing the needles precisely ought to matter.
The largest analysis we have pooled individual data from 20,827 patients in 39 randomised trials of acupuncture for chronic pain. Acupuncture did better than no acupuncture by a clinically visible margin, and better than sham by a small one — about a fifth of a standard deviation — with most of the benefit still there a year later. But the size of the effect was not associated with how the acupuncture was done. What drove the differences between trials was mainly what the control group received; sham needles that actually penetrated the skin came close to the real thing.
That does not say acupuncture fails. It says the benefit does not seem to depend on the precision that a meridian-as-channel account would require. The interstitium hypothesis is not refuted by this. It is simply not needed to explain it.
What this means for body-oriented work
It is fair to say that the interstitium exists, that it is continuous with fascia, and that serious anatomists study the two together. It is fair to say there are small, unreplicated findings that place some acupuncture points in connective-tissue planes — including the part that did not hold.
It is not fair to say that science has confirmed the meridians. It is not fair to say that manual work on fascia acts by moving fluid through the interstitium, flushing it, or “releasing flow”: none of these studies tested anything of the kind. And nothing here supports the idea that fascia or the interstitium store emotions or memories. That claim will attach itself to this research, because the research is new and the claim is looking for a home. It will not have come from the papers.
None of this is a verdict on the language in which bodies are talked about in therapy. The Czech philosopher Pavel Kouba makes the distinction with a glass of wine. “This wine tastes bitter to me” expresses a presence that no one can dispute; only a connection — “the wine is bitter”, “so I am ill” — can be true or false (Kouba 2016, p. 46, our translation). “I can feel it letting go” belongs with the first sentence, and a research paper has nothing in it to refute. In the same book the child psychotherapist Ingrid Strobachová describes what a therapeutic formulation does: it is “an offer to understand something as true. The offer need not be accepted” (Strobachová 2016, p. 229, our translation). So the line does not run between body therapy and science.
Strobachová goes further, in a parenthesis, almost in passing: “psychotherapy as a theoretical discipline is a contradiction in terms” (p. 223, our translation). Therapy is not an unfinished theory that science ought to complete. So the support science can give it does not lie in explaining what happens between therapist and client. Such “explanations” are sometimes offered — and they miss what is essential in the process. What science can do is guard the border: where an offer starts presenting itself as a finding about tissue, what was said above applies.
Measurement needs to be handled with care. On the same page the author asks what effectiveness means in a lifelong or years-long analysis, and what it means in a quick intervention (p. 223). A bounded intervention in one area and at one time can be measured, and fairly easily. What a long-term client of depth therapy is after is something else — the stability and change of how they experience their life. There, the attempt to objectify and “measure” can easily do more harm than good: measurement itself enters the process, and can narrow it to what can be recorded.
The anatomy is a real and good story. It does not need the bridge to be complete in order to be worth telling — and it is better told with the second dye left in.
The sources, graded, with what each one does and does not show, are on the What We Know, and How Well page. Kouba, P., “Pravda v rozumění” [Truth in understanding], and Strobachová, I., “Co je pravdivost v psychoterapii?” [What is truthfulness in psychotherapy?], both in K. Trlifajová, J. Frei et al., Spor o pravdu [The Dispute over Truth], Filosofia, Prague 2016, pp. 43–66 and 223–233. Czech only; the translations are ours.