ISLAMIC
MEDICINE

MANFRED ULLMANN

EDINBURGH

University Press

The movement of the blood

These basic, general physiological doctrines form the foundation for special physiology, that is, the doctrines about the digestion, the blood-movement, sense perception, and so on. Of these, only the doctrine of the movement of the blood will be discussed in detail. To this, an Islamic doctor, Ibn-an-Nafis, has contributed an original essay. But first we shall deal with the system of the movement of the blood in the liver, as presented by al-Majusi.15

The food 'cooked' and prepared in the stomach by the 'first digestion' (al-hadm al-awwal) passes through the pylorus (ho pyloros, al-bawwab) into the duodenum (al-mi‘a dhu l-ithnay ‘ashara isba‘an) and from there into the small intestine (al-mi‘a ad-daqiq). There the veins absorb the chyle (‘usarat al-ghidha’) and transport it through the portal vein (he epi pylais phleps, al-‘irq al-ma‘ruf bi-l-bab) into the liver, where the 'transforming faculty' changes it into the substance of blood. The blood is then brought through the great vena cava (al-‘irq al-‘azim al-ma‘ruf bi-l-ajwaf) to the organs of the body.

Thus the veins (al-‘uruq ghayr ad-dawarib) have their point of exit in the liver.¹⁶ They are of looser, softer substance and only possess one wall. They transport the nourishment from the intestines to the liver, and the blood from the liver to the organs so that these can feed themselves with it. The arteries (al-‘uruq ad dawarib or ash-sharayin) have a double partition. The fibres of the inner layer are striped obliquely and are hard and coarse, the fibres of the outer layer, on the other hand, are horizontally striped and soft. This must be so because the horizontally striped fibres operate the movement of the diastole by means of which the air (al-hawa’) from the heart is sucked

into it. The oblique striped fibres of the inner layer operate the movement of the systole (inqibad) whereby the smoke-like excess (al-fadl ad-dukhani) is pushed out.

The heart, whose flesh is firm, is made up of different layers of fibres and it likewise has its basis in the diastolic and systolic movements.? The heart is surrounded on all sides by the lungs, it has a conical shape, its point inclines to the left because the 'animal spirit' has its seat on this side of the heart; from there too, the arteries radiate outwards and thus one can feel the pulse beat on the left side. The heart has a right and a left ventricle which are separated by a partition. In this partition there is a passage (manfadh) which many people (Aristotle is meant) call a 'third ventrical,’ but this is incorrect.

The right ventricle has two openings. The vena cava which brings the blood from the liver, enters by one of these. This opening is provided with three small membranes, which after the entry of the blood lie on top of one another like a valve, preventing the return of the blood into the vena cava. From the second opening there emerges the vein which has the structure of an artery and which is therefore called 'the arterial vein' (al-‘'irq ash-shiryani).

From the left ventricle of the heart (at-tajwif al-aysar) two arteries go out. The smaller has only a single soft loose wall and is therefore called 'the venous artery' (ash-shirydn al-‘irqi). 'It transports a great part of the blood and pneuma into the lungs so that these can nourish themselves. There it divides into many branches and takes in air. It transports the air from the lungs to the heart in the opposite direction. The second and larger artery is known as the 'aorta' (al-awurta or al-‘irq alabhar) and is divided into two parts of which one goes upwards, the other downwards. The latter is stronger than the ascending one because it has to look after more organs. From the aorta all further arteries of the body branch off.

The two ventricles pulsate in unison, but the left one does so more strongly because it contains a greater amount of blood, animal spirit and innate heat. The right ventricle contains only blood, and only in a small amount. The passage that leads from the right to the left ventricle gradually tapers off in the direction of the left ventricle, so that only the finest constituents of the blood which has come from the liver pass through. The function of the heart consists finally in the fact that it is the storehouse and source of the 'innate heat' (to emphyton thermon, al-harara al-ghariziyya) by which life is maintained.

To understand al-Majusi's account we must free ourselves completely from what is taught today. His statements about the anatomy and physiology of the heart and of the vessels were book-knowledge, already eight hundred years old in his time, and knowledge too which during that period had not been tested against reality because the dissection of the human body was no longer practised. Compared with Galen's account al-Majusi's presentation again shows some simplifications and schematizations, but these cannot be gone into here.18

The heart is a container for the central element of life, the 'innate heat', but it was not realized that it was a mechanical pump. Arteries and veins are correctly described anatomically, but their function is conceived quite differently. The veins carry blood and also, as was seen above, the three other humours, partly as a mixture, but in addition they carry along the 'natural faculties' and the 'natural pneuma'. The arteries also contain blood, but this is finer than the venous blood. Its pure fine vapours mix with the air in the left ventricle which reaches the heart from the lungs by way of the 'venous artery'. Thus arises the 'animal pneuma' which along with the fine blood is transported through the arteries to the periphery of the body. The movement of the blood and the pneumata in the two vessel systems always goes in one direction; it is centrifugal. The blood goes from the liver by way of the vena cava and the branching veins to the periphery, and is there used in the nourishment of the organs; the fine blood and the animal pneuma reach the periphery by way of the aorta, and are there likewise used. Thus the blood in the liver and the pneuma in the heart must be constantly renewed.

A certain rather special role is played by the lungs and the vessels leading to them. Naturally the lung artery was also classified as a vein, because it comes from the right ventricle; but because its anatomical structure shows it to be an artery, it was given the compromise name of al-‘irq ash-shiryani, 'the arterial vein'. It nourishes the lungs with blood. With the vein of the lungs it is the same; it is called ash-shiryan^-al-‘irqi, 'the venous artery', because it comes from the left ventricle but has the structure of a vein. This 'venous artery' has a double function. It transports blood and animal spirit into the lungs in order to nourish these and sustain their vital function. But it also takes air from the lungs and then passes this on to the left ventricle where it is needed to form the animal pneuma. Thus in the 'venous artery' a coming and going of different materials takes place. Such a backwards and forwards movement is not unusual. In the other arteries too a sort of 'exchange of gas' occurs, for we have seen that the arteries, when they are enlarged (namely, in the diastole), absorb the air from the heart, while in the systole they drive out the smokelike waste matter. This, be it noted, has nothing to do with the circulation of the blood as now understood, because sometimes only one vessel or one vein is in action.

The decisive thing in all this is the question of how the blood gets to the left ventricle and into the arterial system. As no communication exists between the 'arterial vein' and the 'venous artery', one must assume a passage in the septum, which guarantees the blood's flow. Galen talks of several invisible pores in the septum; al-Majusi speaks only of one foramen, a simplification which is presumably to be blamed on the Alexandrian teaching manuals.

In the thirteenth century, the Damascus doctor ‘Ala’-ad-Din ‘Ali ibn-Abi-l-Hazm al-Qurashi, called Ibn-an-Nafis,¹⁹ takes up afresh the question of the blood's movement. Ibn an-Nafis, who taught medicine in Damascus and Cairo and died in 1288, wrote several commentaries on Hippocrates in which it appears he explained the material in a dry and scholarly manner. He is chiefly known for an epitome of the Qanun of Ibn-Sina, the Kitab al-Mujiz, which was widely known as a practical handbook and was commented on by Sadid ad-Din al-Kazaruni (d. 1357) and Nafis ibn ‘Iwad al-Kirmani (d. 1449), and in the last century was frequently lithographed and printed in India.

Ibn-an-Nafis not only summarized the Qanun, but also commented on it in a large work. Here he mentions how the blood in the right ventricle is refined so that it is prepared and ready to be mixed with the air:

When the blood has been refined in this ventricle, it must reach the left ventricle where the pneuma (ar-ruh) is formed. But between these two ventricles there is no passage because the substance of the heart is here compact (musmat). In it there is neither a visible passage, as some suppose, nor an invisible passage which would serve to carry the blood through, as Galen thought, because the pores (masamm) of the heart are closely placed here and its substance is firm. Thus this blood, when it has been reach the lungs by the arterial vein so that it can spread out in their substance and mix with the air, so that its finest constituents can be clarified and so that it can then reach the venous artery,from there the left ventricle. 20

With these words Ibn-an-Nafis described for the first time the circulation of the lungs. But he gained his knowledge not on the basis of systematic physiological research but by plain logical deduction derived from the knowledge about the impenetrability of the septum. This must be kept in mind if the significance of his teaching is to be rightly judged. In the Islamic world this teaching has had practically no influence. Only Zayn al-‘Arab al-Misri and Sadid ad-Din al-Kazaruni mention it briefly.²¹ On the other hand the Spaniard Michael Servetus (Miguel Servede, 1509-53) in his book Christianismi resututto which appeared in 1553 and which in the same year brought him to the stake in Geneva, gives a presentation of the lung circulation which resembles Ibn-an-Nafis so strongly that one can hardly reject direct influence. Servetus writes: 'Fit autem communicatio haec non per parietem cordis medium, ut vulgo creditur; sed magno artificio a dextro cordis ventriculo, longo per pulmones ductu, agitatur sanguis subtilis: a pulmonibus praeparatur, flavus efficitur at a vena arteriosa in arteriam venosam transfunditur'²² (‘But this communication is done, not by a passage in the middle of the heart, as is believed by the vulgar (common man); but by a large _____? ventrical to the right of the heart, led along the lungs, the subtle blood is acted upon, prepared by the lungs, ____? is effected until it is transferred by the arterial vein in the venal artery.’) Following on Servetus, Giovanni de Valverde and Realdo Colombo, both in the middle of the six teenth century, described the lung circulation similarly, and after another eighty years the Englishman William Harvey succeeded in 1628 in proving that the blood flows in a complete circle. But in his account too, one problem remained unexplained, namely, the transfer of the blood from the arteries into the veins. It was the microscope that first allowed Marcello Malpighi in 1661 to see the capillaries in the lungs and in the bladder of the frog. Only in this way was the last gap closed, so that the circulation of the blood was proved to be uninterrupted.