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and tend to the conclusion that the difference between animal and plant is one of degree rather than of kind ; and that the problem whether, in a given case, an organism is an animal or a plant, may be essentially insoluble.

VIII.

ON CERTAIN ERRORS

RESPECTING THE

STRUCTURE OF THE HEART ATTRI-
BUTED TO ARISTOTLE.

IN all the commentaries upon the "Historia Animalium" which I have met with, Aristotle's express and repeated statement, that the heart of man and the largest animals contains only three cavities, is noted as a remarkable error. Even Cuvier, who had a great advantage over most of the commentators in his familiarity with the subject of Aristotle's description, and whose habitual caution and moderation seem to desert him when the opportunity of panegyrising the philosopher presents itself, is betrayed into something like a sneer on this topic.

"Du reste il n'attribue à cet organe que trois cavités, erreur qui prouve au moins qu'il en avait regardé la structure.”1

To which remark, what follows will, I think, justify the reply, that it “ prouve au moins" that Cuvier had not given ordinary attention, to say nothing of the careful study which they deserve, to sundry passages in the first and the third books of the "Historia" which I proceed to lay before the reader.

1 "Histoire des Sciences Naturelles," i. p. 152.

For convenience of reference these passages are marked A, B, C, etc.1

Book i. 17.—(4) "The heart has three cavities, it lies above the lung on the division of the windpipe, and has a fatty and thick membrane where it is united with the great vein and the aorta. It lies upon the aorta, with its point down the chest, in all animals that have a chest. In all, alike in those that have a chest and in those that have none, the foremost part of it is the apex. This is often overlooked through the turning upside down of the dissection. The rounded end of the heart is uppermost, the pointed end of it is largely fleshy and thick, and in its cavities there are tendons. In other animals which have a chest the heart lies in the middle of the chest ; in men, more to the left side, between the nipples, a little inclined to the left nipple in the upper part of the chest. The heart is not large, and its general form is not elongated but rounded, except that the apex is produced into a point.

(B) "It has, as already stated, three cavities, the largest of them is on the right, the smallest on the left, the middle-sized one in the middle; they have all, also the two small ones, passages (TETρημévas) towards the lung, very evidently as respects one of the cavities. In the region of the union [with the great vein and the aorta] the largest cavity is connected with the largest vein (near which is the mesentery); the middle cavity with the aorta.

(C) "Canals (rópo) 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. The canals from the heart are uppermost.

(D) "No canal is common [to the branches of the windpipe and those of the vein] (οὐδεὶς δ' ἐστὶ κοινὸς πόρος) but through

1 The text I have followed is that given by Aubert and Wimmer, "Aristoteles Thierkunde; kritisch berichtigter Text mit deutschen Uebersetzung;" but I have tried here and there to bring the English version rather closer to the original than the German translation, excellent as it is, seems to me to be.

those parts of them which are in contact (Tv ovvayu) the air passes in and they [the ópoi] carry it to the heart.

(E) "One of the canals leads to the right cavity, the other

to the left."

(F) "Of all the viscera, the heart alone contains blood [in itself]. The lung contains blood, not in itself but in the veins, the heart in itself; for in each of the cavities there is blood; the thinnest is in the middle cavity."

Book iii. 3.-(G) "Two veins lie in the thorax alongside the spine, on its inner face; the larger more forwards, the smaller behind; the larger more to the right, the smaller, which some call aorta (on account of the tendinous part of it seen in dead bodies), to the left. These take their origin from the heart; they pass entire, preserving the nature of veins, through the other viscera that they reach; while the heart is rather a part of them, and more especially of the anterior and larger one, which is continued into veins above and below, while between these is the heart.

(H) "All hearts contain cavities, but, in those of very small animals, the largest [cavity] is hardly visible, those of middling size have another, and the biggest all three.

(I) “The point of the heart is directed forwards, as was mentioned at first; the largest cavity to the right and upper side of it, the smallest to the left, and the middle-sized one between these; both of these are much smaller than the largest.

(K) "They are all connected by passages (ovvтérpηvra) with the lung, but, on' account of the smallness of the canals, this is obscure except in one.

(L) "The great vein proceeds from the largest cavity which lies upwards and to the right; next through the hollow middle part (dia Toû Koîλov тoû pérov) it becomes vein again, this cavity being a part of the vein in which the blood stagnates.

(M) "The aorta [proceeds from] the middle [cavity], but not in the same way, for it is connected [with the middle cavity] by a much more narrow tube (oúpiyya).

(N) "The [great] vein extends through the heart, towards the aorta from the heart.

(0) "The great vein is membranous like skin, the aorta narrower than it and very tendinous, and as it extends towards

the head and the lower parts it becomes narrow and altogether tendinous.

(P) "In the first place, a part of the great vein extends upwards from the heart towards the lung and the attachment of the aorta, the vein being large and undivided. It divides into two parts, the one to the lung, the other to the spine and the lowest vertebra of the neck.

(Q) "The vein which extends to the lung first divides into two parts for the two halves of it and then extends alongside each tube (opiyya) and each passage (Tpua), 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 (τpîμа) and a vein are absent. The terminations are invisible on account of their minuteness, but the whole lung appears full of blood. The canals from the vein lie above the tubes given off from the windpipe."

The key to the whole of the foregoing description of the heart lies in the passages (G) and (L). They prove that Aristotle, like Galen, five hundred years afterwards, and like the great majority of the old Greek anatomists, did not reckon what we call the right auricle as a constituent of the heart at all, but as a hollow part, or dilatation, of the "great vein." Aristotle is careful to state that his observations were conducted on suffocated animals; and if any one will lay open the thorax of a dog or a rabbit, which has been killed with chloroform, in such a manner as to avoid wounding any important vessel, he will at once see why Aristotle adopted this view.

For, as the subjoined figure (p. 185) shows, the vena cava inferior (b), the right auricle (R.a.), and the vena cava superior and innominate vein (V.I.) distended with blood seem to form one continuous column, to which the heart is attached as a sort

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