It’s still looking good for leech digesta (as the source of “blood” on the Shroud of Turin)

Would your blood still look like this after centuries of storage? Bloodstains, left forearm, top magnification of Durante 2002 image under Shroud Scope, with optimised brightness/contrast to differentiate between blood (plum-coloured) and body image (grey). The yellow-brown stains have still to be explained , but can be accommodated in the ‘medicinal leech digesta’ theory which follows.

Those who have been following my most recent  postings will know that I had a kind of eureka moment a couple of days ago. I refer to the idea that the blood on the Shroud was not applied as fresh human blood – with all the attendant problems of clotting – but as the gut contents of the medicinal leech (Hirudo medicalis) which do not clot (since the leech secretes the potent anticoagulant hirudin).

Between them they could imbibe 10-20 ml of blood at a single sitting – and not need another meal for months, that being how long it takes them (and their resident gut bacteria) to digest the protein of haemoglobin, excreting the watery blood serum first, and later, much later, the still-red porphyrins and free iron.

It was not one of those wild ideas that come out of the blue. In fact it came from asking some very simple questions:

1. What would a medieval monk have used if wanting to dab or paint on blood in strategic locations on the Shroud image of a naked man, so as to make it seem the authentic burial cloth of Christ

2. If real blood, as distinct from a paint or pigment, how could the blood be obtained humanely?

In thinking of an answer to question 2, I initially thought of venesection, aka bloodletting, in which a medieval surgeon used a lancet to nick a vein, but then recalled the other method by which patients deliberately disposed of  a perceived surplus of blood  (usually on a DIY basis!) – using the medicinal leech .

I have been going back through the literature on the Shroud blood, looking all the while at the Shroud Scope images of blood that, as I’ve said previously, looks almost as if painted on.  How could blood be so  dense and “tarry” as to look the way it does, with it congregated on the ribs of the weave, and just a faint pink coloration underneath in places where it seems to have flaked off.  (And why should it flake off anyway if just a “serum exudate” from blood clots as claimed by the late Alan D Adler?)

I have been looking at a picture that Thibault Heimburger MD posted from the Mark Evans photographic archive and comparing it with one of my own blood, dabbed onto linen.  Here is Thibault’s first:

Blood on Shroud (scourge mark, back) from Mark Evans archive/Thibault Heimburger. Note the somewhat patchy distribution, confined to the more superficial locations on the linen weave and its fibres.

Does that look like ordinary human blood to you? Look at the patchy distribution on the weave of the cloth, not dissimilar from body image in appearance (contrary to Thibault’s caption if he won’t mind my saying).

Now look at my blood. Quite a difference – mine looking runny, with no preferential attachment to the ribs of the weave.

Modern human blood, dabbed onto linen after a small DIY accident in the blogger’s home…

Let’s cut to the chase. I believe the Shroud blood came from the gut contents of the medicinal leech, fed on human blood. That is why it looks so “tarry” and why it  largely “stays put” when dabbed on linen, at least the major pigment density (that does not preclude some bleed-through of fainter pigment, e.g. as soluble haemoglobin or haem or protoporphyrin  to the opposite side of the cloth.

Leech digesta ARE presumably tarry, though I have no personal acquaintance myself, given the way that the leech is said to concentrate red blood cells by excreting plasma/serum.  It then progressively breaks down red cell membranes to release haemoglobin as a kind of goo (see references in my previous posting at the end under ‘Background Stuff’) which it then proceeds to digest – just the globin protein we are told, leaving the protoporphyrin  intact, the latter being finally excreted and presumably still red, or red-brown.

Techie bit: so leech digesta provide a spectrum of  red pigments – intact red cells, lysed red cells, intact haemoglobin, partially-digested haemoglobin, free non-ligand bound haems with various molecules attached to the iron atom in place of the imidazole of globin histidine,  and finally free protoporphrin IX and free iron. is it any wonder that Adler and Heller reported an atypical spectrum for Shroud porphyrins, resulting  sadly in some wild speculation re complexation between methaemoglobin and bilirubin. (Bilirubin does not form binary or other complexes – it folds up on itself via internal hydrogen bonding – and is in any case sensitive to light and oxygen – being fairly rapidly bleached).

This is a holding post, just to let my readership (currently some 70 hits a day) know that the leech idea in now my main working hypothesis, and that with each passing hour and day I find more and more snippets in the literature that fit with that hypothesis – and nothing as yet to contradict it.  I intend to produce an updated checklist shortly, showing how “concentrated, semi-digested haemoglobin” from the insides of leeches fed upon human blood can explain a host of details regarding Shroud “blood” that were previously difficult to explain, and which clearly perplexed Adler, Heller and others, Yes, Shroud blood is human blood, but it comes in a tube – commonly referred to as a “leech”- together with  convenience additives,  such as anticoagulants –  all pre-processed and pre-packaged.

Leech nutrition (that’s a leech that has been fooled into thinking that a vial of warn blood with a membrane is human flesh and blood). It’s puncturing the membrane, ready to gorge five times or more its own body weight.

Less like ink from a  runny marker pen (see my earlier post) – more like an artist’s oil paint, and applied as such, to simulate blood flows from a crown of thorns, spear wound in side, scourge marks, nail wound etc etc.


PS:   This blog should be seen as a scientific odyssey, or,  less grandly, a learning curve, warts an’ all. As I’ve said previously I believe it is the first time that a scientific investigation has been reported from the very first hesitant step  on the internet in real time, starting last December  on my ‘science buzz‘ site. I have now posted some 80 or so times, 56 of them on this, my main site. I still don’t claim to be an expert on the Shroud (and don’t care for that term anyway – I am a Shroud investigator/critical commentator using such data and other resources that are in the public domain). One thing’s for sure. There is a lot of “received wisdom” out there in the Shroudology literature – some of it purporting to be science – which to my now better-informed mind is frankly absurd and simply agenda-serving, indeed agenda-pushing.

Here’s a cautionary word for the promoters of pseudo-scientific claptrap:  all it requires is proof that that blood on the Shroud is medieval or later, and what are you left with – a piece of cloth with a faint image of a naked man – without wounds, without any evidence of having been crucified?  Remind you of anything? Yup, the Man on the Lirey Pilgrim’s badge – the earliest known representation (circa 1355) of the Shroud of Turin. Herringbone weave, yes. Double image, frontal and dorsal heads apposed, yes.  Unequivocal evidence of having died by crucifixion – no… (See my previous posting re the Lirey badge and the probable link to Crusaders and/or tortured and then publicly-executed Knights Templar, notably Jacques de Molay and Geoffroi de Charney).

Postscript: that Shroud Scope picture at the top is now a source of intense interest to this investigative blogger (or should that be blogging investigator). Those red-brown stains that accompany the plum-coloured “blood” have intrigued me for some time. What are they? What do they represent? If one were dealing with “simple” human blood, simple but for the effects of ageing, or simple but for complex theories re clot retraction, one could speculate that the brown represents some kind of fractionation, with serum (brown) separating from blood pigments (red or plum). But the entire idea of serum is problematical (the subject shortly of another post) given the confusing STURP literature, with talk of the “blood” being in reality a “serum exudate”, while at the same time referring to “serum halos” which are only well visualised under uv light. There seems to be “serum” and “serum”…

My leech digesta theory opens up an array of new perspectives in attempting to explain the heterogeneity of those bloodstains. With leech digesta one is dealing with at least 3 components – ingested human blood (in varying degrees of digestion), the leech’s own digestive secretions (lipases, proteases etc) and finally the symbiotic bacteria in the leech gut, with two strains predominating, that assist the leech with its digestion of haemoglobin. Maybe it is one of more of the latter two components that are responsible for the red-brown staining. Note that it is restricted to where one sees plum-coloured blood, i.e. it is part of the same stain, not two adjacent or superimposed stains. One is looking at a mixture – the components of which were transferred to the linen simultaneously – as distinct from a serial “touching up” scenario.

Alternatively, the red-brown stain represents a “scab” of leech digesta, with a wide range of components, most of which has flaked off over the centuries to leave a porphyrin (plum-coloured) stain.

Postscript: added 6th April 2013

Fame at last. After having this posting largely ignored on The Other Site for months, Kelly Kearse has finally addressed the leech proposition, albeit in a strange mixture of interest and gentle sarcasm.

After sitting tight and waiting to see what killer points would be raised in objection (none, I think it safe to say) there was an opportunity to add some new thinking as to what precisely makes the blood a permanent bright-red colour after its lengthy sojourn in the leech gut.

Answer? Nitrite and/or nitrogen monoxide, NO? Here’s my full comment:

April 5, 2013 at 6:04 pm | #62

Alan D.Adler was one of STURP’s top chemists, a porphyrin specialist, someone who could be relied upon to recognize a red colour that was simply too bright to be aged blood. Adler knew about meth(a)emoglobins and other oxidised haems, he knew about the crucial importance of the precise electronic configuration of the iron centre to properties like colour, uv/visible spectra, fluoresence etc. What’s more he reported the isolated porphyrin to have an aytpical spectrum. So what did he do? Say it was just a trick of the light, a artefact of photography? No, he was so taken with the various anomalies that he felt obliged to propose new chemistry to explain his findings – namely that novel association between methaemoglobin and bilirubin that would account for those eternally red bright bloodstains.

Yet as soon as one dismisses Adler’s creative chemistry, and substitutes what one believes is more conventional chemistry – what happens? Folk pile in to deny the existence of the very effect that so preoccupied Adler. No, there’s nothing unusually red about the blood, they say, it’s all a figment of your imagination, and Adler is conveniently forgotten in the rush to repel the new threat, to retreat to a new defensive position.

For blood to have retained its bright red colour, one can reasonably assume that the iron centre has been retained at the centre of haem, probably as oxidized iron (III) in place of the original iron (II), but with a new electron donor or donors bonded onto the iron, maintaining its electron configuration in the form that keeps it bright red. Quite what the new donors might be is anyone’s guess. Carbon monoxide has been suggested, but I’m inclined to think it might be nitrite ion, NO2-, or nitrogen monoxide (NO, a stable free radical). The first of those is responsible for giving ham and bacon and other cured meats their stable long-lived pink colour, so it’s possible a similar kind of chemistry might operate between aged haems and decomposition products say of the arginine in globins. Where would this take place? Inside a leech of course, which is where one of us came in…


Here’s some background info gleaned just this morning from the Web that confirms my hunch that nitrite ion and/or NO would react with methaemoglobin to form a red adduct, comparable to the kind of chemistry used in meat curing that involves treatment of meat and its myoglobin (a simpler version of haemoglobin found in musscle) with nitrites:

Nitrites in turn become nitric oxide, which cures the meat.

 1. Nitrite and/or nitrate are used in curing meat to counteract the undesirable effects of salt upon color.

2. Not only is the color of fresh meat protected from degradation, but the pigments react with nitric oxide to produce the stable pigments characteristic of cured meat. These pink pigments are important to the acceptability of most processed meat products.

3. Both nitrite and/or nitrate are used in meat curing for color stabilization. The end result is the same in either case, although the pathway for stabilization of color by nitrite is more direct. Since nitrite reacts quicker and less is required for color stabilization, it is being widely used in place of nitrate.

4. Many processors prefer to use a combination of nitrite and nitrate, which gives a source of additional nitric oxide should the nitrite be depleted during curing. They believe the slower release of nitric oxide from nitrate gives them an additional safety factor over nitrite alone. Nevertheless, many highly successful operators use nitrite alone with excellent results.

5. Trends have been toward decreased use of nitrate by the industry.

6.  Nitric oxide is the active ingredient that combines with meat pigments. Although not being proven conclusively, all evidence suggests that the original combination of nitric oxide is with the oxidized pigments, metmyoglobin and methemoglobin. The best proof for this step is the fact that the pigments in sausage become characteristically brown after adding the cure, but after heating have the characteristic pink color of cured meat.

7.  An alternate pathway for production of the stable pink pigment is possible, in which nitric oxide-metmyoglobin is not formed. In this case, myoglobin is oxidized to metmyoglobin, which ­is reduced back to myoglobin before combining to form nitric oxide­myoglobin.

8. The end result is the same regardless of the pathway; nitric oxide reacts to produce the desirable and stable pink pigment of cured meat.

9. Any hemoglobin remaining in the meat would undergo essen­tially the same series of reactions and also give a stable pink pigment.

10. Since nitrite reacts quicker and less is required for color stabilization, it is being widely used in place of nitrate.





About Colin Berry

Retired science bod, previous research interests: phototherapy of neonatal jaundice, membrane influences on microsomal UDP-glucuronyltransferase, defective bilirubin and xenobiotic conjugation and hepatic excretion, dietary fibre and resistant starch.
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2 Responses to It’s still looking good for leech digesta (as the source of “blood” on the Shroud of Turin)

  1. Pingback: Shroudie-Alert: Day 12: time now to write that long-overdue letter to the Royal Society… | The Turin Shroud: medieval scorch? Separating the science from the pseudo-science…

  2. Pingback: Dear Royal Society. Time maybe to take a hard line on those who peddle Turin Shroud pseudoscience? | The Turin Shroud: medieval scorch? Separating the science from the pseudo-science…

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