Book 3
15
And secondly [the presence of these anastomoses has been assumed] from the fact that, of the two orifices in the right ventricle, the one conducting blood in and the other out, the formerHe means the tricuspid orifice. cf. p. 121, note 4. is much the larger. For, the fact that the insertion of the vena cava into the heartThe right auricle was looked on less as a part of the heart than as an expansion or insertion of the vena cava. is larger than the vein which is inserted into the lungsThis vein (really the pulmonary artery) was supposed to be the channel by which the lungs received nutriment from the right heart. cf. p. 121, note 3. suggests that not all the blood which the vena cava gives to the heart is driven away again from the heart to the lungs. Nor can it be said that any of the blood is expended in the nourishment of the actual body of the heart, since there is another veinthe coronary vein. which breaks up in it and which does not take its origin nor get its share of blood from the heart itself. And even if a certain amount is so expended, still the vein leading to the lungs is not to such a slight extent smaller than that inserted into the heart as to make it likely that the blood is used as nutriment for the heart: the disparity is much too great for such an explanation. It is, therefore, clear that something is, taken over into the left ventricle.Galen's conclusion, of course, is, so far, correct, but he has substituted an imaginary direct communication between the ventricles for the actual and more roundabout pulmonary circulation, of whose existence he apparently had no idea. His views were eventually corrected by the Renascence anatomists. cf. Introduction, pp. xxii.-xxiii.
