Evolving human beliefs and knowledge of blood

 

Blood has always played a highly symbolic role in a number of diverse human societies, regardless of the geographic location, cultural belief system, or degree of social and scientific development of the people involved. This is largely because humans have long recognized that this vital fluid, with its life sustaining properties, forms a common bond linking them intricately to each other, both physically as well as to the range of emotions and events that make up the cycle of life, such as birth, initiation, humiliation and death. However, as the secrets that concealed the true nature of this amazingly complex substance were uncovered through scientific inquiry, so people have had to confront and amend their former beliefs about blood and its place, both mystical and practical, in our lives. Now, while the context within which blood is presently viewed and managed may have changed considerably, it is still worth reviewing some of the old misconceptions and beliefs that existed, as these provide an illuminating insight not only on past human behaviour, but possibly also into present subconscious thoughts on the topic.

 

Many of the prevailing Western attitudes and customs relating to blood can be traced to the early civilizations that evolved around the Mediterranean Sea. To the first truly thoughtful humans, blood had mysterious life giving properties that were both transferable and consumable, resulting in the spread of many bizarre stories as to its use. In ancient Greece, one of the tales recounted by Ovid detailed how Aeson drank the blood of his son, Jason, in order to regain his youthfulness, while the Egyptians displayed similar attitudes towards the rejuvenating properties of blood, although in their case, they felt satisfied simply by bathing in it. During the golden age of Rome, circus gladiators would drink the blood of their slaughtered opponents, in the belief that this allowed them to absorb part of the life force of their victims, and thereby remain victorious in combat. Meanwhile, in Judea, the early followers of Jesus Christ commemorated his death by drinking wine, which symbolised the blood that he shed, in the belief that this act allowed them to commune with Him, and thereby gain eternal life [1]. Amongst other early societies in the wider world, blood also had important social properties. Throughout South America for example, indigenous tribes believed that demons could be exorcised through venesection (the bleeding of a persons veins), while in some of the more advanced local empires, the sacrifice of human life accompanied by the spilling of blood was believed to be a necessary requirement for appeasing the will of the gods. In contrast to such wanton bloodletting, the Mongol tribes in central Asia believed that royal blood was so precious that special measures were implemented to ensure that none of it ever spilled upon the soil of the earth [2].

 

Despite being attributed with having special positive powers, blood has also been viewed as an object of disgust, and has consequently been widely used as a mechanism for discrimination against people with "different" characteristics. In a social sense, blood has always been used as an unseen barometer of class, with socially “superior” people allegedly being deemed to have better, or “bluer”, bloodlines than the lesser respectable classes of people. It has also been used as a means of racial and ethnic discrimination, where  people with “white” blood were kept apart from those with “black” blood, while a more notorious example involved the Nazi effort to propagate the purity of an “Aryan” nation by eliminating those with “impure” blood, such as Jews and Gypsies. Finally, the fact that women have to undergo monthly menstrual cycles has often been viewed with distaste by men, and has served as a useful tool for the imposition of social, legal and religious restrictions upon them [3].

 

The first significant milestone in haematology was probably made by the Roman physician Galen, who discovered that the arteries contained blood, and not air, as was previously believed. With this knowledge, he was to advocate the use of a medical process known as bleeding, which involved the application of medical instruments or leeches to the veins of a patient in order to “cleanse” away any impurities that were diagnosed as being present in the body [4]. Once this discovery had been made though, haematology remained largely in the doldrums for a number of centuries, with the next major scientific advance only occurring in 1616, when Thomas Harvey discovered that blood circulated within the body, thereby renewing interest into how different substances could operate within the blood stream. The first recorded blood transfusion was carried out in 1665 when, under the influence of the renowned Christopher Wren, the British anatomist, Dr Richard Lower, transfused blood from one dog directly into another [5]. Two years later, the first transfusion into a human being took place when the French scientist Jean Baptiste Denis transfused blood from a lamb into a 15-year-old boy [6]. Although this experimental transfusion failed with the death of the patient, it was to trigger a spate of copycat experiments elsewhere in Europe (with similar results), which only ended once a papal decree and bans imposed by national authorities had been issued on further tests of this type.

 

As a consequence of the prohibitions on experimentation, rudimentary general medical knowledge, and the continuing popularity of bleeding, it was a long time before further substantial progress in haematology took place. Indeed, the next major development only occurred about 150 years after the first experimental transfusions, when Dr James Blundell started developing an apparatus for directly transfusing blood. By 1818, his work had progressed to such an advanced stage that he was able to carry out the first human-to-human blood transfusion. Subsequently, the number of transfusions tentatively started to rise, although many remained unsuccessful, with patients suffering from adverse reactions (including death) caused by unidentified factors. It was only in 1900 that the primary cause of this problem was finally uncovered, when the Austrian researcher, Dr Karl Landsteiner, disproved the then common assumption that blood, per se, was a fluid homogenous to all people by demonstrating that there were in fact 4 major blood groups (the so called ABO groups), each of which had unique biological characteristics that affected their compatibility with other blood types [7]. Once this landmark discovery was made, the remaining obstacles in haematology gradually fell away, with landmark new discoveries in recent years being restricted mainly to the classification of minor blood types and the solving of issues of a practical nature, although the evolution of genetic science suggests that a whole new series of scientific breakthroughs might be made in future

 

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