One of the biggest questions surrounding the strange white fibrous structures found in the dead may finally have an answer.

For years, there was an obvious explanation.

Perhaps the strange white, rubbery structures being pulled from blood vessels by embalmers weren't really a phenomenon of the living at all.

Perhaps they formed after death.

Blood stops moving. It coagulates. The body changes.

Case closed.

Except researchers Bruce Rapley and Dr Matt Shelton went looking.

And what they found inside these structures makes that explanation considerably harder to sustain.

(WATCH DR JOHN CAMPBELL DISCUSS -VIDEO)

They found evidence of flowing blood

Rapley and Shelton examined what they call Anomalous Intravascular Casts — long, elastic, sometimes branching structures recovered from blood vessels.

Some measured up to 25 centimetres.

Their histological examination found something particularly important:

Lines of Zahn.

These are microscopic layers associated with clot formation in flowing blood.

That distinction matters enormously.

After death, circulation stops.

A structure displaying genuine features of formation under flowing blood conditions therefore carries evidence that at least part of it developed before circulation ceased.

Rapley and Shelton put it plainly:

"their presence provides strong evidence that these structures formed in vivo, at least in part, under flowing blood conditions."

In vivo.

In the living body.

And suddenly this becomes a very different story.

Because the question was never merely: "What are these things?"

The more important question was:

When did they form?

If they were simply the product of coagulation after death, they might be unusual — but they couldn't have harmed the person while they were alive.

If they were forming inside functioning blood vessels before death, we have another question entirely.

What were they doing there?

Rapley and Shelton's paper reports elongated, lumen-filling structures, some branching through the architecture of blood vessels.

Their conclusion is cautious: morphology alone cannot determine what caused them.

But their discussion raises an obvious clinical concern.

If these structures arise during life, the authors write, their physical properties "may influence vascular obstruction, hemodynamics, tissue perfusion and resistance to thrombolysis."

Read those first three again:

Vascular obstruction.

Hemodynamics.

Tissue perfusion.

In ordinary language:

Could they obstruct blood vessels?

Could they alter the movement of blood?

Could they reduce the delivery of blood to tissues?

Now we are getting to the question that matters.

Did they kill?

We already know that seriously restricting blood supply can be deadly.

That principle isn't controversial.

The human brain, heart and other organs require blood and oxygen. Cardiovascular medicine is built around the consequences of vessels becoming narrowed or obstructed.

So if unusual, lumen-filling structures were forming inside blood vessels while these people were alive, could they have restricted circulation sufficiently to contribute to death?

It's an obvious question.

It is also one the present research does not yet answer.

And that distinction matters.

Rapley and Shelton have presented evidence about when at least part of these structures formed.

They have not established that the structures caused the deaths of the people from whom they were recovered.

Those are two different scientific questions.

But answering the first makes the second considerably more urgent.

John Campbell saw the implication immediately

Discussing the research, Dr John Campbell reaches the same uncomfortable point.

If the Lines of Zahn finding is confirmed, he reasons, part of these structures must have formed during life.

He then says they were therefore:

"probably partly responsible for killing the individual."

But Campbell immediately adds:

"We need that confirmed."

Quite right.

We should not turn a hypothesis into a fact simply because the hypothesis is alarming.

But neither should we pretend the hypothesis isn't alarming.

Because the old question was:

Are embalmers simply seeing something that forms after death?

The Rapley–Shelton findings provide evidence against that simple explanation.

The question now becomes:

What happens when these structures form in the living?

And these don't appear to be ordinary clots

There is another important development.

A separate 2026 study by Daniel Santiago, Greg Harrison, Miklós Veres, Mark File and Dennis Planner subjected samples of white-to-pale fibrous intravascular casts to Raman microspectroscopy and other analyses.

They reported unusual protein characteristics and concluded that the analysed casts represented atypical protein aggregates distinct from conventional post-mortem thrombi.

So two different lines of investigation are beginning to converge on an important point.

Rapley and Shelton report histological evidence suggesting at least partial formation under flowing blood conditions. Their paper is presently a preprint and has not undergone journal peer review.

The separate Raman study reports biochemical and structural characteristics distinguishing the samples it examined from conventional post-mortem thrombi.

That still doesn't tell us why these structures formed.

It doesn't establish how common they are.

And it doesn't establish that they caused anyone's death.

But "they're just ordinary post-mortem clots" is becoming a much less satisfactory explanation for the particular samples being studied.

So what caused them?

We don't know.

That question must remain separate from everything above.

The Raman study had no linked donor histories and specifically states that no causal relationship to an exposure, infectious agent, vaccine or therapeutic intervention could be inferred from its data.

Rapley and Shelton likewise say further biochemical and molecular work is required to determine the mechanisms underlying these structures.

So there is no scientific basis here for declaring a cause.

There is, however, ample reason to investigate one.

The question has changed

For several years, photographs and embalmer testimony could be dismissed with a fairly simple objection:

You found them after death. How do you know they weren't created by death?

Now we have histology.

And within that histology, Rapley and Shelton report Lines of Zahn.

Their interpretation is unambiguous:

strong evidence of formation in vivo, at least in part, under flowing blood conditions.

That doesn't finish the investigation.

It begins the important part.

Because if unusual fibrous structures are forming inside people's blood vessels while they are alive, medicine needs to establish:

How often?

In whom?

Why?

How quickly?

Can they be detected?

Do they restrict blood flow?

And most importantly:

Did they contribute to these people's deaths?

We don't yet know.

But now there is considerably more reason to find out.

Watch the full investigation

In the video below, Dr John Campbell examines the emerging research into these unusual structures and the evidence surrounding their formation before death.

Read the Rapley–Shelton research for yourself:

Morphological and Histological Characterisation of Anomalous Intravascular Casts (AICs) — Bruce Rapley & Dr Matt Shelton.

And then ask the question that now matters:

If they were forming while people were alive, what were they doing to them?

Read the Rapley & Shelton paper

Read the Raman spectroscopy paper