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Galen's unambiguous and informed testimony that Asclepiades was a void theorist in the Epicurean vein is thus corroborated implicitly by Calcidius, and indirectly by two further independent sources. That Asclepiades posited void is also presupposed by his use of an atomist argument for the existence of void, and by the fact that another aspect of his theory of matter, viz. the perpetual motion of the onkoi, which is only precisely paralleled in Epicurean physics, is conceptually dependent on the existence of void according to both Epicurus and Aristotle. The next section will be devoted |
In this way we say that Asclepiades used three hypotheses for establishing the obstruction which produces fever: the first, that there are certain theoretical pores in us, differing from each other in size;... S.E. M 3.5 [pp. Like the onkoi, the pores fall below the level of sense perception, and their existence has to be inferred with the use of reason, that is, they are intellectu sensae, or in Greek λόγῳ θεωρητοί (νοητοί in Sextus). Also like the onkoi, they differ from each other in size and |
But Lonie isolates a different usage, of which he finds examples first in the ps.-Aristotelian Problemata, referring not 'to the normal channels of the body,' but 'to the interstices of bodily substances which are regarded as porous.' Although Lonie sees the origins of this latter usage in the Stratonic conception of discontinuous void, there is no reason to consider its general sense theory-specific. 40 One might broadly typify the first usage as emphasizing the physical object or structure through which matter may 38) Vallance (1990), 56; see also 115, where, referring |
travel, but the second as implying primarily the mere absence of a physical obstacle to the passage of matter. Modern analyses of Asclepiades' doctrine of pores sometimes translate πόρος in ways which seem to presuppose the former usage, for example with terms such as 'canaux,' 41 or 'canali.' 42 But we must be clear about what sorts of assumptions such translations involve, and how our interpretations of the evidence are conditioned by them. If, of course, one thinks of a πόρος as a channel or vessel, and thus as a physical structure in the former sense, then one is likely to read |
44 ἀραίωματα is also used by Sextus Empiricus, who wrote on Asclepiades' doctrine, 45 and by the ps.-Galenic 41) E.g. Pigeaud (1981). 42) E.g. Casadei (1997). 43) On the possibility that the even more suggestive term κενώματα was used by the ps. author of the Introductio sive Medicus. 46 We may note, too, that πόροι and ἀραιώματα are neatly paralleled by the only two attested Latin terms for |
47 ἀραίωμα, of course, cannot mean 'channel' or'vessel,' etc., or refer to a physical structure of this sort, but it certainly can, or rather does, mean 'gap' or 'interstice.' Our understanding of the pores should thus be informed by the meaning of both terms used to describe them: ἀραίωμα effectively rules out the former usage of πόρος described above, viz. as 'channel,' whereas it coincides precisely with the latter, viz. as 'gap.'Additionally, Epicurus used the term πόρος in essentially the same way as I am suggesting it was |
49 He is not suggesting that the eidola have a specially conforming channel or duct through which they pass, but merely 46) Sextus uses both terms, once each: M. 3.5 (quoted above), and M. 8.220: Ἀσκληπιάδῃ δὲ ὡς ἐνστάσεως νοητῶν ὄγκων ἐν νοητοῖς ἀραιώμασιν. The ps.-Galenic author of Int. likewise uses both terms, once each, at 9 [14.698 K. = p. |
49) On the passage of eidola through a πόρος, see also Epic. fr. 24.46.13-16 Arr. According to Sedley's convincing reconstruction, there is no reference to πόρος at fr. 31.4.1-4 Arr. = fr. 8 col. iv Sedley (1973). that, given their size, they have free passage, without physical obstacle. These passages or routes clearly refer to the free passage of atoms through void, but the same concept of free passage is at work in his description of fine water passing through suitably sized πόροι in the |
Cel. Pass. 1.15.128, p. 94 Bendz This ubiquitous permeability clearly describes the complete porosity of the human body, in a way which is prima facie much more suggestive of a conception of the pores as gaps between onkoi, rather than their conception as channels or vessels, which would seem to imply that some parts were interconnected as others were not (so at least is the basic notion when one thinks of visible channels, for example blood vessels or nerves). The opportunities for passage are everywhere, and everything is interconnected. In this way, then, Caelius' complexio corpuscul |
53 Given this interpretation, we can also better understand how the differences in size and shape of the pores come about. There is an exact parallelism between Caelius' descriptions of the pores and the onkoi. At On Acute Diseases 1.14.105 and 106 respectively, he describes the corpuscula as'magnitudine atque schemate differentia,' the viae likewise as'magnitudine atque schemate differentes.' The precise repetition of this description within a few lines, and the fact that the pores result from the combination of the corpuscles, could be taken to imply |
Accordingly, the Asclepiadean pore is an imperceptible gap or opening between onkoi within the solid structure of the human body through which other onkoi may pass. These gaps vary in shape and size depending on the shape and size of the delimiting onkoi. We may also assume that temporal variation in the size and shape of the pores is caused by the fact that the onkoi are in perpetual motion. If this interpretation is correct, then it can also be shown that these features of Asclepiades' pores are precisely paralleled by the Epicurean doctrine of void gaps between |
It is of course a central tenet of atomism that the atoms of which all perceptible objects are composed are separated from each other by void. This entails that all apparently solid objects in the visible realm are in fact permeable. At a general level in his explication of Epicurean physics, empirical observation of the permeability of apparently solid forms of matter constitutes part of one of Lucretius' arguments for the existence of void. 54 At a more specific level, on the other hand, when Lucretius turns to his explanation of the physical processes associated with animate beings, and indeed with pseudo-animate objects such as |
The existence of openings or interstices in solid objects, as we have seen, is a consequence of the intervals of void which must exist between individual atoms. In the context of his explanation of how various living things have differing tastes, Lucretius comes to analyse the relationship between the interstices and atoms more fully: 54) Lucr. 1.346-57, esp. 346-47, 'praeterea quamvis solidae res esse putentur,/ hinc tamen esse licet raro cum corpore cernas' ('Besides, however solid things may be thought to be, |
In its basic features, then, this account precisely parallels the descriptions of Asclepiades' pores: in both theories, primary particles in perpetual motion, when they come together to form solid, perceptible objects, nevertheless have empty gaps or interstices between them which differ in their size and shape depending on the shapes and sizes of the confining particles. These interstices also allow the passage of primary particles through them. Given these precise and comprehensive parallels between the two theories, including the corresponding Epicurean and Asclepiadean usage of the term πόρος, and since Epicurean interstices represent void, |
An answer can also be given to the question why the sources consistently refer to the pores in discussing his theory, rather than void per se, despite the fact that void must have been what they represent. I suggest that, in the principally medical contexts with which our sources are concerned, Asclepiades was for the most part simply not interested in void per se, but only in void as manifested within the human body. This is well illustrated by the purpose for which he uses the atomists' argument from growth as discussed above. We have no evidence that Asclepiades was concerned with wider cosmological issues in his theory; his |
As a brief epilogue, some comment may be thought necessary on the possibility that Asclepiades instead posited a form of Stratonic disseminate 59) Leith (2009) ; see above n. 4. microvoid. 60 The ancient sources, it will be noted firstly, point to no such link. The idea rests on the assumptions firstly that Asclepiades' theories were derived in some way from Erasistratus' principle of 'the following (of matter) towards the area being vacated' (πρὸς τὸ κενούμενον ἀκολουθία, |
Galen, our only direct source on the subject, informs us that Asclepiades posited the existence of Epicurean-style void. As I hope to have shown, we have no reason to doubt Galen, and several different reasons to believe him. I conclude that Asclepiades' pores contained large-scale void, and that it was in virtue of void that his onkoi were able to move at all. Given this conclusion, there can be little doubt that Asclepiades took his doctrine of void, and of void spaces within solid bodies, directly from Epicureanism. The fact that Asclepi |
In the 5 years between 1962 and 1967, an empirical foundation was laid for clinical organ transplantation, using chemical immunosuppression based on azathioprine and prednisone, with or without ALG. This was at first a time of wild and frequently unwarranted enthusiasm, which was then succeeded by a dozen years of deepening despair. The I-year survival of cadaver kidney grafts through the 1970s remained frozen at 50%, and even in successful cases, this kind of treatment was more like a disease than a cure. Although long survival after liver, lung, heart, and |
At the darkest and most unexpected moment, a mounted torch-bearer appeared in the distance. The torch was cyclosporine; the bearer was Jean Sore\. and the horse was the Sandoz Corporation. How the next steps were taken by Roy Caine and his English colleagues is the material of legends. Suffice it to say, both the patients and those who cared for them were liberated from a terrible bondage. There have been improvements in treatment since then, How could a single person have such an impact, particularly in this modern era in which individual scientists are increasingly viewed as mere cogs in a multidisciplinary research machine |
The journey started with the purification of erythropoietin (EPO), a glycoprotein hormone produced by the fetal liver and then by adult kidneys. The protein was purified in 1977 1 and the gene was cloned in 1985. 2 At that time, it was known that EPO was produced in response to a low blood oxygen concentration. However, it was not known how EPO was regulated by low oxygen. Semenza and his colleagues found that a region located on the 3' enhancer of EPO, currently known as the Hypoxia Response Element (HRE), was responsible for |
Kaelin's group at Harvard made major contributions to deciphering this regulatory mechanism. Based on his clinical experience as an oncologist, Kaelin was aware that most kidney tumors that lose expression of the von Hippel-Lindau (VHL) tumor suppressor are highly vascularized. When he and his group found that VHL forms a complex with Elongin B and C and CUL2, homologs of yeast ubiquitin ligase proteins, 10, 11 he hypothesized that the absence of VHL could lead to VEGF stabilization and subsequent increased vascularity. Indeed, he soon discovered |
This modification turned out to be prolyl hydroxylation on the proline 564 residue, which is essential for the recognition of HIF-1a by the VHL complex. Recognition of the modification leads to the ubiquitination and subsequent proteasomal degradation of HIF-1a. This breakthrough demonstrated that oxygen-dependent prolyl hydroxylation is key for mammalian oxygen sensing. However, this led to another question, namely, what was responsible for the HIF-1 oxygen-dependent hydroxylation. Ratcliffe, Kaelin (with the Conaways) and Steve McKnight all found the same answer |
Importantly, their work opened up the important field of research focused on mammalian oxygen sensing. At present, there are close to 70 enzyme family members that may depend on oxygen for their functions besides prolyl hydroxylases. 25 In fact, some of the enzymes involved in epigenetic regulation, including KDM5A (also known as RBP2) histone demethylase, which identified by Kaelin and Yi Zhang, 26 were recently shown to be oxygen sensing enzymes. 27, 28 It remains to be determined how other enzymes would work in oxygen sensing, and if the effects |
The forms and meanings of early modern teaching diagrams have remained largely unexamined by cultural historians. This situation, however, is slowly changing, especially in light of work that treats scientiic diagrams as pictures. 5 In addition to this, the growth of digital culture in recent years has slowly begun to erase the division hitherto drawn between timeless works of art and everyday pictures. Instead of being seen as sedentary objects that exist outside time and space, pictures are now seen as objects that were recognized, made, and circulated in many ways that required different modes of access. 6 In this chapter I wish to build on |
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