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Galen
On Respiration and the Arteries
By David J. Furley, J. S. Wilkie PRINCETON UNIVERSITY PRESS
Copyright © 1984 Princeton University Press
All rights reserved.
ISBN: 978-0-691-08286-8
CHAPTER 1
THEORIES OF RESPIRATION BEFORE GALEN
a. Empedocles, the Sicilian School, and Plato
Most of the work of the early Greek physiologoi is lost. It must count, therefore, as a piece of good luck that one early theory of respiration was described in a surviving work of Aristotle, and that his description was supported by a direct quotation of twenty-five consecutive lines of hexameter verse. Empedocles was the author; Aristotle quotes him in his De respiratione, Ch. 7, 473 b 9 (fr. 100 of Empedocles, in Diels-Kranz Fragmente der Vorsokratiker). The date of Empedocles' work cannot be determined exactly, but 450 B.C. is probably correct within a margin of ten or fifteen years.
Thus do all things breathe in and out: for all, there are tubes of flesh, left by the blood, stretched over the outermost part of the body, and over the mouths of these the exterior surface of the skin is pierced through with close-set furrows, in such fashion that blood lies hidden within, but a clear path for air is cut through by these channels. When the delicate blood runs away from these, air seething with fierce flood rushes in; when it flows back, it breathes out in return.
The italicized phrases, translated unambiguously above, are ambiguous in Greek, as will be explained. But one thing is clear and undisputed: in Empedocles' theory, blood and breath move in the same vessels of the body — "tubes of flesh, left by the blood" in the sense that the blood that they contain regularly flows out of them, leaving room for air to enter. They are alternately filled with blood and breath. It is of great importance for the understanding of Greek physiology to observe that from the earliest recorded theory the two systems of blood flow and respiration were linked. If we are to understand the conceptual framework of Greek theory, we must put aside the modern notion that the only link between them is the oxygenation of the blood in the lungs.
But what exactly was the physiology and anatomy of blood and breath as conceived by Empedocles? This is a very difficult question to answer because of the ambiguities referred to above. The chief difficulty is the word "[TEXT NOT REPRODUCIBLE IN ASCII]" in the fourth line: it is translated above as "skin," but it may also mean "nostrils," and there is some evidence to show that Aristotle, our sole source for the fragment, understood it in this latter sense. In classical Greek prose, "[TEXT NOT REPRODUCIBLE IN ASCII]" would normally be interpreted as "nostrils." It is possible, with ingenuity, to make some sense of the opening lines on the assumption that Empedocles used the word in that sense. The words "[TEXT NOT REPRODUCIBLE IN ASCII]" translated above as "over the outermost part of the body," can be read as "deep inside the body," and "[TEXT NOT REPRODUCIBLE IN ASCII]" translated above as "the exterior surface of the skin," can be read as "the furthest ends of the nostrils." On this interpretation, Empedocles asserts that tubes of flesh lead from deep inside the body to the back of the nostrils, and where these tubes meet the nostrils there are perforations so small that air can pass through but blood cannot.
In my opinion, this view must be rejected. There is no such set of perforations at the back of the nostrils, nor has any supporting evidence of belief in them been found in other Greek writers. The trachea, which is the likeliest candidate for a "tube" leading from deep inside the body to the nostrils, is not normally filled with blood, nor is there any reason why Empedocles should have thought it was. Moreover, this is a forced interpretation of the Greek phrase "[TEXT NOT REPRODUCIBLE IN ASCII]" and this way of reading the lines makes poor work of the simile of the clepsydra that follows.
It is much more probably that we have in this fragment a theory of breathing through pores in the skin. The "tubes of flesh" are simply the blood vessels, some of which are indeed "stretched over the outermost surface of the body," just under the skin. "Over their mouths," according to Empedocles, the skin is pierced with small holes, through which breath but not blood can pass. As blood withdraws from the surface, so breath enters, and as blood returns, breath leaves through the same pores.
It is likely that Empedocles chose the ambiguous word "[TEXT NOT REPRODUCIBLE IN ASCII]" deliberately. If he had wanted a nonambiguous word for "skin," "[TEXT NOT REPRODUCIBLE IN ASCII]" could have been substituted without any other change in the hexameter. The skin, in his theory, is functioning like the nose, an obvious and undisputed organ of respiration, and he uses a pun to draw attention this claim.
The notion that blood vessels "breathe" through pores in the skin is an integral and quite important part of Galen's theory of blood flow and respiration, as we shall see. By Galen's time it was a theory of some precision: the arteries draw in air through the skin in diastole and expel waste through the skin in systole, and this process is part of the system that maintains moderate heat in the body. It is said that skin-breathing is a characteristic feature of Sicilian medical doctrine, and we shall see in later paragraphs that there is evidence for attributing it to Philistion and Diodes, as well as to Plato, who adopted much from the Sicilians. There are some grounds, however, for thinking that the doctrine spread to other schools, even before the time of Galen. Jaeger attributes it to Aristotle, but I have found no evidence for it, and some evidence against it. Galen finds no inconsistency in attributing to Erasistratus the view that air is emptied out of the body after passing through the arteries — presumably through pores in the skin, as in his own theory, although he does not say so. Anonymus Londinensis attributes skin-breathing to Hippocrates; so Wellmann's view, based on De morbo sacro, that the Coan school denied skin-breathing may need qualification. But we will return to these controversial matters below, in the sections of this Introduction that deal with the various schools.
It must be observed that Empedocles' theory of respiration was not intended as a purely physiological theory, in any sense. Breath was either identical with or closely related to one of the four cosmic elements that formed the basis of his whole world picture. Blood, according to fragment 98, is made of these four elements, and "blood around the heart in men is thought" (fr. 105). There is evidence that the proportions of the mixture were crucial to thinking. So it is a reasonable conjecture that breathing was supposed to serve the purpose of preserving the right balance, in some way, between the elements in the blood. It is possible that the balance was especially a matter of the right heat, but the evidence is not conclusive. In the present context, however, we need go no further into the speculations of Empedocles.
Philistion, mentioned by Galen in De usu respirationis 1 (K IV 471), along with Diodes, as maintaining that respiration is for the sake of the preservation of the innate heat, is relatively unknown except for the account of his theories given by the medical papyrus called Anonymus Londinensis. In date he was contemporary with Plato.
In a summary of Philistion's views on the causes of disease, Anonymus Londinensis says he divided the causes into three classes: the elements, through excess of one of their "powers"; the condition of our bodies; and external causes. He explains the second of these: "The condition of our body is a cause of disease in the following way. When, he says, the whole body breathes well and the breath passes through unhindered, health is the result. For breathing ([TEXT NOT REPRODUCIBLE IN ASCII]) takes place not only by way of mouth and nostrils, but also over all the body" (xx 42–47, transl. Jones). It has been argued that this is not sufficient evidence to attribute skin-breathing to Philistion, but that seems unnecessarily sceptical; it is only the belief that skin-breathing is an eccentric doctrine that would suggest looking for another interpretation.
At least there can be no doubt that Plato's Timaeus includes skin-breathing in its physiological doctrine, and that breathing is closely connected with blood flow as in Empedocles.
In Timaeus 79 b1–e9, the explanation of breathing begins from the proposition that there is no void space into which a thing may move. Hence the air expelled by breathing out displaces its neighbor, and that displaces its neighbor, until the last in the circular chain replaces the air that was breathed out. That is to say, air enters the chest and lungs through the skin to replace the air breathed out through the nose and mouth, and when this air leaves again and moves outward through the body, by a circular thrust it pushes air in through the nose and mouth. Having thus set out the general principle, Plato gives a causal explanation. The natural heat of the body, harbored in the blood and the vessels ([TEXT NOT REPRODUCIBLE IN ASCII]) has a natural tendency to seek the company of its kin outside the body. There are two directions it can take to the outside, one "by way of the body" ([TEXT NOT REPRODUCIBLE IN ASCII]), the other by way of the mouth and nostrils. When it moves toward one of these exits, it pushes air around into the other; that which goes out is cooled, that which enters is warmed, and this change in heat causes a reversal of flow.
The physiology of the Timaeus closely connects blood flow, respiration, and nutrition. Food in the stomach is worked on by the heat of the body and thus transformed into blood (80 d), with which the blood vessels are filled. The blood is washed around the body so as to nourish all its parts by the respiratory movement of air in the blood vessels. Respiration is caused mechanically, then, by the movement of "fire" toward its like, and the cooling action brought about by this motion, which puts it into reverse. The reciprocating motion causes air to be first introduced into the vessels of the body and then expelled by the same route; inspiration through the mouth and nostrils takes place at the same time as expiration through the pores of the skin, and vice versa. The reciprocating motion of the air in the vessels moves the blood, and thus nourishes the body.
There are two particularly striking features of this theory, both of which are significant in the history of Greek physiology. First, blood is regarded quite unambiguously as food. This was an idée fixe among Greek thinkers, and was probably more than anything else responsible for their failure to understand that the blood circulates through the body and returns to its starting point. The idea survives intact in Galen, who had "his mind firmly rooted in the older notion that blood is a sort of warm nourishing soup in which all the parts are amply bathed." Second, it will be noticed that the heart plays no part in Plato's account of the distribution of blood. It is the movement of the air that moves the blood, not the pumping action of the heart. The heart is indeed mentioned in the Timaeus as "the fountain of the blood that courses over all the limbs," and as the "knot of the vessels" (70a–b). This is not, however, in the context of nutrition, but of functions of the three parts of the soul. The heart is the center of the thymos or spirited part; when appropriate messages reach the heart from the rational part of the soul, the thymos boils, and the emotional message, "felt along the blood," as we might say, is carried to all the limbs. This must imply that the heart is at the focal point of all the vessels, so that it has lines of communication to them all. There seems to be also a suggestion, not fully developed, that the heat of the thymos is a cause of the movement of blood outward from the heart. But it would be a mistake to regard Plato as having taken a position in the controversy that developed later among biologists as to whether the heart is the "origin" of the blood vessels. Plato's account of the anatomy of the blood vessels is quite fanciful, and bears little relation to scientific knowledge, ancient or modern.
We have now mentioned three theories of blood flow and respiration, of which the last is reported in more detail than the others. Whether or not they are all the same theory, handed down from Empedocles to Philistion and Plato, is not clear. There is no reason to think that Empedocles held the Platonic theory of the tripartite soul, and he could hardly therefore have written in just the same way about the heart as the seat of the thymos. Though it has been strongly denied, it is probable that Empedocles' theory of breathing included the notion of reciprocal breathing in and out through the skin and the nose and mouth. There is also nothing inconsistent, in the fragments of Empedocles and Philistion, with the Timaeus theory of heat as the cause of the reciprocal motion.
It is interesting that Galen criticizes the "circular thrust" theory of Plato's Timaeus at some length in his De placitis Hippocratis et Platonis VIII 9 (K V 713–16). Plato attributed everything to pushes instead of to attraction ([TEXT NOT REPRODUCIBLE IN ASCII]), and this was a great mistake, in Galen's view. He quotes three examples of attraction to show what he means: a man can suck water up through a tube by sucking the air out of the tube first; babies suck milk from the breast; bellows draw in air when expanded. The thorax, likewise, on expanding, draws in air from outside through the nose and mouth, and the arteries on expanding draw in air from outside through the skin. (Attraction, [TEXT NOT REPRODUCIBLE IN ASCII], is one of Galen's favorite concepts, and we shall say more about it below, in connection with his criticism of Erasistratus.) Galen adds two more criticisms. Plato ignores the element of choice in breathing, which is obvious, since one can hold one's breath at will; and he also ignores the lack of synchronization between respiration and pulse. Galen thus assumes that breathing through the skin is Plato's explanation of the observable pulse in the arteries — a doubtful assumption.
b. Diogenes of Apollonia
Brief mention should be made here of one more of the pre-Socratic philosophers: Diogenes of Apollonia (probably not the Cretan Apollonia but the Milesian colony on the Pontus), who lived some time in the mid-fifth century B.C., perhaps a little later than Empedocles. He is not, indeed, a central or essential figure in the background to the dispute between Erasistratus and Galen which forms the chief subject of this book, because his theories did not have much of a following. But he has two claims to a mention here: he is the author of the earliest surviving Greek anatomy of the blood vessels (if we discount Aristotle's brief mention of the mysterious Syennesis of Cyprus in Historia animalium III 2, 511 b 24ff.), and he attached truly astonishing properties to the air that he supposed to be distributed by the vessels.
His anatomy of the vessels is recounted in the Aristotelian Historia animalium III 2, 511 b 30ff. No distinction is made between arteries and veins: the word used throughout is phlebes. There is no mention of the pulse. Nothing is said about the function of the vessels in this passage, and very little about the contents: the description occurs in the context of an account of blood, however, and it appears to be assumed that their business is the distribution of blood. What is striking is that the heart plays no special role. Aristotle includes Diogenes among those who place the origin of the vessels in the head (513 a 11), but the quoted description seems to have them originate vaguely in the middle. The main feature of Diogenes' vascular anatomy is a pair of major vessels, one left and one right, with big or little branches spreading to all parts, and a pair of smaller vessels passing from the head through the neck and going down the arms to the hands alongside the major ones. Although this doubling is not clearly maintained in the rest of the passage, it may suggest that Diogenes "had observed, without knowing it, the double system of veins and arteries" (Harris, The Heart, p. 25).
(Continues...)
Excerpted from Galen by David J. Furley, J. S. Wilkie. Copyright © 1984 Princeton University Press. Excerpted by permission of PRINCETON UNIVERSITY PRESS.
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