History of leeches
Practice of bloodletting for medical purposes most likely dates back to the Stone Age. Evil spirits inhabiting human body were believed to cause various illnesses, hence blood withdrawal was considered an effective treatment. In pre-Colombian America, Aztecs believed that during bloodletting evil spirits would leave the human body. In the Maya kingdom, the practice of bloodletting was assigned to a special group of healers. Records concerning use of leeches for medical purposes date back to the beginning of civilization. In ancient Egypt, blood withdrawal was recommended as means of expelling ‘spoiled blood’. During these procedures a skin of a patient was incised or pierced and a leech was attached. In ancient Greece, blood withdrawal was believed to cure contagious diseases. Oftentimes, blood was let from the elbow wrist or veins found on the feet, in the back of knees or even on the tongue. Such therapy was practiced by Hippocrates (460-377 B.C.), he did not however assign it any particular effectiveness. Herophilos of Chalcedon (2nd-3rd century B.C.), one of the finest physicians of the Alexandrian school, recommended bloodletting for removing the excessive moisture from the body. The oldest writing that mentions leech is the Bible. In the 30th chapter of the proverbs of Solomon (Proverbs 30:15) it stands: “The leech has two daughters. ‘Give! Give!’ they cry. “There are three things that are never satisfied, four that never say, ‘Enough!’. In the original language of the Bible, the reference to leech was made using the term Alukah. This Hebrew word is an equivalent of the phrase ‘to be bound’ and most probably was chosen for it deftly expresses the fact that leech is bound to the skin, alike people are bound to their destination. The mentioned passage presents a negative image of the attributes of leeches. This only proves the fact, that their habits and behaviour were already well-known at that times. The aggressiveness of leeches inhabiting swamps and pools of Palestine which were seen to fiercely attack legs, tongues and nostrils of horses and other animals, aroused fear among people. Never-satiated, the leeches sensed the potential victims using their receptors sensitive to temperature, sweat, blood, water movements and changes of the air humidity and carbon dioxide content caused by breath of the approaching host. They attacked their victims whether they were satiated (their crop was filled with indigested blood) or not. Up to this day, there is a deep conviction among the rural populations that nine hungry leeches can bite a horse to death. Leeches suck blood so frantically that during the meal they stop responding to any external stimuli, cutting off the posterior part of their body might not be enough to interrupt the feeding. Around 140 C.E. a Roman physician Antyllus (author of a manual of bloodletting) for the first time conducted such experiment. In 1759, it was confirmed by Laurence Hiester (author of ‘A General System of Surgery’) and in 1968 by Galun and Kindler. The hematophagy leech will sooner die from overfeeding than give up on sucking blood. The oldest reference describing ways of leech application comes from the late Hellenic period and was written by Nicander. He depicts ‘as the bloodsucking worms are attached to those parts of the body, which shall be relieved from blood and juice stasis’ and recommends to leave them until they are satiated and fall off on their own. Term used to the describe the ‘bloodsucking worm’ inhabiting swamps was derived by Nicander and Theocrite from the word mulgeo (milk). A Roman physician Galen (131-201 C.E.), alike his Greek predecessors believed in the concept of humours, according to which it was the balance of four body fluids (blood, phlegm, black and yellow bile) that played the crucial role in regulating bodily functions. It was Galen who for the first time marked the 45 sites on the human body which he believed were the best for bloodletting, determined the frequency of procedures and the amount of blood that should be drawn. He was convinced that bloodletting, known also as the breathing veins, is helpful in treating both serious illnesses and minor ailments. Another fine physician and surgeon of the Antiquity, Antyllos (first half of the 2nd century C.E.), described the technique of letting blood from veins and arteries. Romans have also for the first time used the present term Hirudo (leech), Plautus, Cicero and Horatio among them. Pliny the Elder (Caius Plinius Secundus) in his work Historia naturalis depicted a bloodsucking leech. Chinese writings from the first century C.E. provide a relatively detailed description of medicinal leeching. Numerous references can be also found in Sanskrit, Persian and Arabic literature. The first Western documentation of medical use of leeches is the poem Alexipharmaca written by Nicander of Colophon (200-130 B.C.). In the Islamic countries, despite the common fear of bleeding, bloodletting was one of the most popular medical practices. Avicenna (980-1037 C.E.) recommended it as a remedy for toothaches. ‘Attaching leeches to the roots of teeth or letting blood from the cup placed below the tongue, or yet putting shattered cups below the chin’ was supposed to bring pain relief.
The ancient humoral theory proved to be applicable in the European medical practices during the Middle Ages. In order to restore the balance of bodily fluids magic spells and laxatives were applied, when those failed – the blood was let. Bloodletting was usually conducted by a barber-surgeon, however, permission and presence of a physician during the procedure were required. Most often, the practice was performed in public baths, where both healthy and sick people spent hours resting in baths and tubs. Allowing men and women to the same rooms oftentimes caused scandals and was a reason for closing the facilities. Bloodletting was considered to be most effective when performed right after the bath and physicians recommended incising nearly any available vein. It was applied for both, therapeutic and prophylactic purposes, in the course of serious illnesses blood was let repeatedly. During the Black Plague, bloodletting was believed to reduce the natural temperature of the body and remove the ‘poison’. Numerous superstitions and customs were connected with attaching leeches and letting blood. The one that was most strictly observed concerned ‘days bad and less fortunate, not appropriate for letting blood and very dangerous for such procedures’. Proceeding according to special anatomic-astrological charts was believed to be a guarantee of successful therapy. In monasteries, bloodletting was a regular practice performed 4 to 5 times a year, before the Lent, after the Easter and Whitsunday, at the end of the summer and before the Advent. Also, a conviction pervaded that people wanting to live in sexual purity, especially men, shall systematically remove the so-called ‘hot blood’. In spite of many significant achievements in the field of medical sciences in the 17th and 18th centuries, knowledge and skills of an average physician were relatively poor. The concept of four humours dominated in the medical practice and the diseases were believed to be caused by ‘corruption’ or ‘concussion’. Hence laxatives, enema and bloodletting seemed most appropriate forms of treatment, oftentimes bringing disastrous results. Ludvig XVIII had undergone 47 bloodletting procedures within one year. A prominent French philosopher and astronomer, Pierre Gassendi (1592-1655) died after he had undergone the 14th procedure. Withdrawing excessive amounts of blood was a common practice sanctioned by the conviction that human body contains about 25 liters of this fluid. Leeches proved to be very useful on delicate and sensitive sites of human body where using instruments of the time was impossible, hazardous or difficult because of the limited access to the area. A medical text from 1634 enumerates gums, lips, nose, fingers or even ‘the mouth of the womb’ as some of those sites.
The popularity of medicinal leeching reached its peak in the 18th and 19th centuries. About 80 millions of leeches were used annually in France, Russia and England. It is worth mentioning that in France and Russia incomes from the sales of leech exceeded incomes from the crop sales. European medicine at the turn of 18th and 19th centuries was dominated by skepticism and therapeutic nihilism. Followers of those trends rejected their faith in medical intervention, questioning diagnostic accuracy and effectiveness of both, recommended procedures and administered medications. Francois J. V. Broussais (1772-1838), professor of medicine and director general of Val de Grâce hospital in Paris, became the leading representative of the French skeptical school. According to him, the majority of illnesses was the result of ‘irritation’ and ‘plethora’ of the digestive tract and so, they required an anti-inflammatory treatment a fine example of which was bloodletting. He recommended leech attaching as an alternative to the complicated procedure of venesection. In this way, he treated all kinds of medical conditions including contagious, neurological and mental illnesses. At times, he would let blood from one patient for up to 32 times and when he himself had a runny nose, he would conduct the procedure upon himself for up to 7 times. The faith in infallibility of Broussais and popularity of leeches among doctors made them a therapeutical factor par excellence. Each patient admitted to a French hospital was first attached 20 to 30 leeches and only then, diagnosed. In 1824 ‘à la Broussais’ fashion became very popular among elegant Frenchwomen who wore clothes decorated with jewellery items imitating leeches. Obviously enough, these were not the only areas of life where leech came to be useful. For example, during the wedding night, blood released from a leech was used to cover up the fact that the bride was not a virgin bringing good luck to the marriage and pleasing the husband. Trade in medicinal leeches became an attractive and major source of income. One person, primarily women, could collect up to 2500 leeches daily by wading through waters and swamps and letting them attach to their legs. Leech collecting has been also described by Friedrich Nietzsche in his work ‘Thus spoke Zarathustra’ written between 1883 and 1884. In the fourth part of the fourth chapter, he wrote: For the sake of the leech did I lie here by this swamp, like a fisher, and already had mine outstretched arm been bitten ten times, when there biteth a still finer leech at my blood, Zarathustra himself! The increasing demand for leeches made its population disappear almost entirely. Various government programs have been introduced to encourage entrepreneurs to develop swamps, lakes, ponds and streams in order to breed leeches. An official proposal was made to designate old horses for leeches to feed on. All these initiatives proved insufficient when confronted with the huge demand thus leeches had to be imported heavily from other countries. From the notes of Napoleon we have learnt that 6 millions of leeches were imported from Hungary every year for the needs of his army. It is sometimes said that the French lost during this period more blood due to leeching, than in the course of all the Napoleon’s wars. Influence of Broussais in France was significantly limited by Pierre Louis (1787-1872) and his static method. By compiling a considerable number of observations, he provided evidence indicating that the popular belief in a beneficial effects of bloodletting was basically groundless. Years later, results of the research conducted and presented by Louis were confirmed by a an excellent Polish clinician, Józef Dietl (1804-1878). Dietl was a representative of the Vienese school of skepticism who later became a professor at the Medical College in Cracow. He fought against the traditional treatment based on bloodletting and promoted the scientific research on the origins of different medical conditions. After 1830 the practice of leeching for medical purposes started to decline as the mass-production of medications was launched. In 1884 a professor of physiology at National School of Medicine for Wales, John B. Haycraft discovered that blood consumed by the leech does not coagulate nor decay in its digestive tract.
20th CENTURY – NOWADAYS
By the end of 1950, professor F. Markwardt had isolated from the blood of a leech a pure anticoagulant, the hirudin. Today, leeches are known to contain over one hundred organic chemical compounds all of which have very complex structure and reveal many desirable therapeutical properties. With these discoveries, the popularity of medical leech resurfaced and is know a subject of great interest among medical research centers, clinics and hospital which seek for innovative methods of treatment. Medicinal leech is nowadays considered a living miniature of pharmacological laboratory.