Totalling up to 10 percent of our bodyweight, blood is a water based suspension and solution of many ingredients, each serving a specific purpose. The principal ingredients are as follows :

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The cells

Erythrocytes / red cells

               These cells are produced by the bone marrow. They have the particularity of not containing a cell nucleus during their "adult" stage, that is to say after 3 or 4 days of circulation in the blood vessels. Normally they live for about 4 months before being destroyed and recycled in the the spleen where their contents are released into the blood. Each cubic millimetre of blood (one millionth of a litre) contains about 5 millions of these red cells. We have around 5 litres of blood, and so have about 25 thousand billions red cells in our bodies at any time. Your body creates and destroys two and a half millions of them each second of your existence.

               Each red cell is a round disk, about 7.5 thousandths of a millimetre in diameter, and concave on each side. If we could put them side by side in a thin red line, the red cells in our body would form a chain, 7 microns wide, and 175,000 km long, passing three times around the earth. (Don't try it).

               The red cells owe their name to their red component, haemoglobin, a macromolecule with a molecular weight of 68,000, roughly spherical in shape, and 60 angstroms in diameter ( 6 millionths of a millimetre). 95 percent of the haemoglobin is a colourless protein called globin, and 5 percent is a porphyrin compound containing 4 linked pyrrole rings, each containing an iron atom in the ferrous ionic state (Fe++). It is on these iron atoms that the oxygen attaches for transportation. (Oxygenated haemoglobin is often known as oxy-haemoglobin. It is said to be what gives arterial blood its bright red colour). By contrast, the CO2 radicals transported by the haemoglobin back to the lungs are not transported on the iron, but on an amine group on the amino acids of the globin (notably Leucine).

               When red cells are destroyed in the spleen, their constituents are liberated, and the resulting free haemoglobin in the blood is quickly broken down into :

• Globin, which is digested by the liver where the amine groups are stripped off and recycled for the synthesis of other proteins.
• Haem which is split into :
  • Iron, which will be used to synthesise new haemoglobin molecules.
  • Porphyrin, which is broken down into bilirubin and eliminated by the liver as urine and bile. It is from bilirubin that plasma and serum get their yellow colouration, and it is an abnormal excess of bilirubin that gives that characteristic orange colour to the skin of jaundiced people.

               Apart from diseases, the two main destroyers of red cells are : 

• The spleen, which destroys red cells as they reach the end of their useful life.
• Shocks (either trauma from outside the body, or interior, e.g. heart valve malfunction). 

               When the destruction of red cells is abnormally large, the concentration of bilirubin in the blood increases. (Hyper-bilirubinaemia can be an indication of haemolysis).

Leucocytes / white cells

               They are 1000 times less numerous than the red cells. The have a fundamental role in the defence and immune system of the organism, whether this be immediate (polynuclear), or delayed (lymphocytes). They are usually made in the thymus or lymph glands and fall into two classes :

• Granulocytes, including stem cells (les cellules souche) and myoblasts which give the polynuclears such as neutrophils (which destroy bacteria), eosinophils (which react against allergies and infections), and basophils (which help control coagulation and inflammation.
• Lymphocytes, including stem cells (les cellules souche) and lymphoblasts, are situated in the bone marrow and lymph tissue, (ganglions, amygdala, Peyer's patch, spleen, thymus). They give the small and medium mononuclears.
• Monocytes, including stem cells (les cellules souche) and histioblasts, which are situated in the reticuloendothelial system (bone marrow, spleen, ganglions). They give monocytes, histiocytes, plasmocytes, mastocytes.

               Although indispensable to everyday life, they have no particular role in the Passion and we will leave them behind for others, while we pass quickly on.

Thrombocytes or Platelets

               These small platelets are only a third of the diameter of the red cells. Generated in the bone marrow, we find about 300,000 platelets in each cubic millimetre of blood. They play a fundamental role in the coagulation of blood anywhere that a blood vessel is cut. There they cluster at the damage zone, and control clotting and healing by activation of prothrombin, which generates thrombin enzyme activity, which transforms the fibrogen into fibrin.

               Not surprisingly, an excess concentration of these platelets in the blood encourages thrombosis (formation of a blood clot inside a blood vessel), and an insufficient concentration reduces the blood's ability to form clots and so increases the risk of haemorrhage.

Plasma          

               It is composed of water (92%), proteins (70 grammes per litre), organic compounds other than proteins, and mineral salts.

               The proteins are essentially albumins (42 g/l) and globulins (24 g/l). Amongst the globulins, the best known are the immuno-globulins (also called antibodies), and fibrinogen (which plays an important role in coagulation).

               The non-protein organic compounds are, in decreasing order of concentration : lipids (4 to 6 g/l), cholesterol (2 to 2.5 g/l), phospholipids (1.5 g/l), glucose (1 g/l), free amino acids (500 mg/l), urea (300 to 400 mg/l), lactic acid (100 mg/l), uric acid (45 mg/l), creatinine (30 mg/l), bilirubin (5 to 6 mg/l), ammonia (1 to 2 mg/l). Also present, in trace amounts, are hormones, vitamins, enzymes...

               The elements, ions and radicals of the mineral salts and electrolytes found in the blood are : Chlorine (3650 mg/l), Sodium (3300 mg/l), bicarbonate (1650 mg/l), Potassium (180 to 190 mg/l), phosphates (95 to 106 mg/l), Calcium (100 mg/l), sulphates (45 mg/l), Magnesium (18 to 20 mg/l), Zinc (3 mg/l), Copper (1.2 mg/l), Iron (1 mg/l), Iodine (0,07 mg/l).

               Particular attention can be given to the Iron, for it is one of the elements strongly present on the Shroud (along with Calcium and Strontium). The body of a man of 70 kilogrammes normally contains 4 to 5 gm of iron, of which 3 gm are in the haemoglobin, 1.5 gm in the liver, bone marrow and spleen, and the rest spread between the myoglobin, cytochromes, and enzymes (like peroxydase and catalase). Iron in the serum/plasma (outside of the red cells) is no more than 5 mg overall.

Analysis          

               Now that we know better what is in the blood, lets ask ourselves how we can detect the presence of blood, or its components, on the Shroud, and understand better what the traces have to tell us.

The red cells : 

               It is sometimes possible to see them directly, for their shape and diameter is characteristic. However, whilst red cells have apparently not been directly observed on the Shroud, at least one of their constituents has -- haemoglobin, which can be identified through its characteristic spectral absorption bands. The spectral absorption bands of haemoglobin are :

• The Soret band at 410 nanometres (at the limit of the visible violet in the spectrum).
  When John Heller and Joe Gall analysed spectroscopically a red crystal taken from the cloth of the Shroud, they obtained a very strong absorption band between 425 and 395 nanometres, and which peaked at 400.
  Note that the co-efficient of extinction of the porphyrins at this wavelength is 250,000.
  
• The Stokes band at 555 nanometres, for reduced haemoglobin.
  
• A band at 576 nanometres and another at 540 nanometres for oxy-haemoglobin.
  S. Pellicori and his collaborators worked on the Shroud. In places where the Shroud was marked by what most people believe are blood stains, they found a strongly absorbent band at 400-420 nm, another at 530-580 nm, and a third at 625 nm.

               The deductions are easy to make. The pinkish marks on the Shroud, that most people assumed to be bloodstains, have tested positive for haemoglobin.

Iron

               X-ray fluorescence revealed the presence of Calcium, Strontium, and Iron, and that (apart from the additional, very high concentrations of Iron at the blood stains) they were regularly distributed on the Shroud.
Note that at the blood stains, Fe++ was measured at 0.02 to 0.04 mg/cm2, compared with 0.01 mg/cm2 at the face, and elsewhere outside of the blood stained areas. [Work by A. Morris and his collaborators]

               Ultra violet photography shows clearly that the cutaneous lesions are rimmed with an UV-fluorescent halo, even though the lesions themselves do not show this fluorescence. (Porphyrin in the blood, as we have just seen, has an enormous extinction coefficient.)