“In oviparous animals, such as birds, and in quadrupeds which are oviparous, the one half of the lung is widely separated from the other; so that it appears as if they had two lungs. And from being single, the windpipe becomes (divided into) two, which extend to each half of the lung. It is fastened to the great vein, and to what is called the aorta. When the windpipe is blown up, the air passes into the hollow parts of the lung. In these, are cartilaginous tubes (διαφύσεις) which unite at an angle; from the tubes passages (τρήματα) traverse the whole of the lung; they are continually given off, the smaller from the larger.” (Book i. 16.) That Aristotle should speak of the lung as a single organ divided into two halves, and should say that the division is least marked in man, is puzzling at first; but the statement becomes intelligible, if we reflect upon the close union of the bronchi, the pulmonary vessels and the mediastinal walls of the pleuræ, in mammals;[38] and it is quite true that the lungs are much more obviously distinct from one another in birds. Aubert and Wimmer translate the last paragraph of the passage just cited as follows:— “Diese haben aber knorpelige Scheidewände, welche unter spitzen Winkeln zusammentreten, und aus ihnen führen Oeffnungen durch die ganze Lunge, indem sie sich in immer kleineren verzweigen.” But I cannot think that by διαφύσεις and τρήματα, in this passage, Aristotle meant either “partitions” or openings in the ordinary sense of the latter word. For, in Book iii. Cap. 3, in describing the distribution of the “vein which goes to the lung” (the pulmonary artery), he says that it “extends alongside each tube (σύριγγα) and each passage (τρῆμα), the larger beside the larger, and the smaller beside the smaller; so that no part (of the lung) can be found from which a passage (τρῆμα) and a vein are absent.” Moreover, in Book i. 17, he says— “Canals (πόροι) from the heart pass to the lung and divide in the same fashion as the windpipe does, closely accompanying those from the windpipe through the whole lung.” And again in Book i. 17— “It (the lung) is entirely spongy, and alongside of each tube (σύριγγα) run canals (πόροι) from the great vein.” On comparing the last three statements with the facts of the case, it is plain that by σύριγγες, or tubes, Aristotle means the bronchi and so many of their larger divisions as obviously contain cartilages; and that by διαφύσεις χονδρώδεις he denotes the same things; and, if this be so, then the τρήματα must be the smaller bronchial canals, in which the cartilages disappear.