Galen’s description differed altogether from that of Aristotle. He tells us expressly and somewhat contemptuously that ‘it is no marvel if Aristotle erred in many anatomical matters, a man who thought forsooth that the heart in the larger animals had three chambers’.[207] Galen always describes the heart as having but two chambers, the right and left ventricles, a wholly subordinate part being assigned to the auricles. These latter were regarded as safety-valves, expanding to hold superfluous blood when the chambers of the heart to which they correspond become overfilled.
No third ventricle is described by Rhazes or Haly Abbas,[208] but Avicenna, in his Canon, makes an effort to combine the views of Aristotle and Galen. Speaking of the anatomy of the heart (lib. iii, fen. xi, chap. 1) he describes the ventricular portion as follows: ‘In the heart are three cavities, two large, and a third as it were central in position. So that the heart has [a] a receptacle [the right ventricle] for the nutriment with which it nourishes itself—this nutriment is thick and firm like the substance of the heart; [b] a place where the pneuma is formed [the left ventricle], being engendered of the subtil blood; and [c], thirdly, a canal between the two.’[209] A somewhat similar account is given in Constantine’s translation of Isaac.[210] The idea soon crept into European medicine, for in a Pisan MS. dating from the first half of the thirteenth century[211] a crude figure of a three-chambered heart is to be found (Fig. 21).
The first translator of the Canon of Avicenna, Gerard of Cremona, whose work appeared towards the end of the twelfth century, improved on his original. ‘In it [the heart] are three ventricles; two are large, and the third as it were between, which Galen called the fovea or non-ventricular meatus, so that there may be a receptaculum for the thick and strong nourishment, like to the substance of the heart, with which it is nourished, and also a storehouse for the pneuma (spiritus) generated in it from the subtil blood. And between the two are channels or meatuses.’[212] Henri de Mondeville (died about 1320), by going direct to Galen, avoided some of the errors of Avicenna, with whom, however, he still describes three ventricles.[213] Mondino does little but copy the Arabian, whom Manfredi also follows.
We may terminate our description of the mythical third ventricle by quoting from Bartholomew the Englishman. His encyclopaedia written about 1260 was translated into English in 1397, and printed by Thomas Berthelet[214] in the 27th year of the reign of Henry VIII (1535), when Bartholomew’s work was still extremely popular. Berthelet’s rendering runs as follows:
‘And the hert hath ij holownesses, one in the left syde, that cometh sharpe: and one in the ryght side, that is within: And these two holownesses ben called the wombes of the hart. And betwene these two wombes is one hole, that some men call a veyne, other an holowe way. And this hole is brode afore the ryghte syde, and streyte afore the left syde. And that is nedefulle to make the bloode subtyll, that commeth from the ryght wombe to the lefte, and so the spirite of lyfe may be bredde the easelyer in the lefte wombe.’
In order to understand why all these authors invoked the existence of the third ventricle, regarded by some of them as a passage between the other two, we must turn to the physiological beliefs of the age. It must be recalled that before the demonstration of the circulatory movement of the blood a certain amount of communication was believed to exist between right and left ventricles. The complicated nature of the ventricular cavities and the intricacy of the columnae carneae promoted the idea of the presence of minute passages in the interventricular septum. Even so astute an observer as Leonardo da Vinci considered that ‘the ventricles are separated by a porous wall, through which the blood of the right ventricle penetrates into the left ventricle, and when the right ventricle shuts, the left opens and draws in the blood which the right one gives forth’ (Plate [XXXVIII b]).[215]
Fig. 22. From Johannes Adelphus, Mundini de omnibus humani corporis interioribus menbris Anathomia, Strassburg, 1513. The diagram shows the two lateral ventricles and the ‘central’ ventricle. By a printer’s error the letters c and d are transposed. The arteria adorti is the aorta, the arteria venalis the pulmonary vein, the vena chilis the vena cava, and the vena arterialis the pulmonary artery. The auricles are ignored, as is frequently the case in works of the period, and the pulmonary veins are represented as opening directly into the ventricles.