On behalf of the Council, I send you Christmas Greetings.
HSS Lecture Meetings in the Crypt Room at St John’s Church, 8.15 pm.
December 16th Explosions from the Sun by Louise Harra (University College London).
January 13th A Neuroscientist’s View of Metastatic Disease by Professor Mustafa Djamgoz (Imperial College).
February 10th Human Embryos, Stem Cells and Cloning by Dr Joyce Harper (University College London).
March 17th Science, History, Art and Computers by Professor Robert Weale (HSS).
Some of our older members may well have problems with their joints. I myself take a non-steroidal anti-inflammatory drug (NSAID) for my knees, but I am aware that prolonged use can lead to stomach and renal problems. Another drug often used is a ‘cox2 inhibitor’ but one of these, VIOXX has recently been withdrawn as a side-effect is an increased risk of heart attack! The other main option is a knee replacement, but this involves major surgery and is more complex than a hip replacement. A recent article in Nature by Helen Pilcher reports studies which suggest the use of an ancient treatment for such osteo-arthritic problems – leeches.
The use of leeches in human medicine has a long history: images of leeches have been found on the walls of ancient Egyptian tombs and it has been reported that Marcus Aurelius used them for blood-letting 1500 years later. After the 19th century they fell from favour though, surprisingly, they are still used post-operatively in plastic surgery units.
The studies  reported a trial of 24 people with knee problems. Up to 6 leeches were applied for about an hour till the leeches fell off gorged with blood. Control patients were given an anti-inflammatory gel twice a day for a month. One week after treatment started, the leech-treated patients reported a 64% reduction in pain, compared with 17% for the controls. Michalsen and Dobos have since carried out a study with 400 patients, not yet published, and claim even better results.
It is not easy to validate such claims as they are based on the patients’ own reports and consequently open to auto-suggestion. Nor is yet clear what precise bio-chemical action may be responsible. The leech certainly injects complex proteins into the patient prior to sucking out the blood and some of these may have an anti-inflammatory effect. But nor is it certain that the pain arises solely from inflammation as Nsaids do not work for all patients. There may be a vascular disorder and the leech saliva may act as an anti-coagulant.
At present the verdict is “not proven”, so no leeches for Christmas, thank you!
 Nature, 4 Nov 2004, pages 10,11. Back
 Michalsen A et al., Ann. Intern. Med.139, p 724 – 730 , 2003. Back
Probably the most remarkable thing about the earth’s atmosphere is the high proportion of the gas oxygen --- about 21%. No other planet in the solar system has more than a trace. Oxygen is also a very corrosive element; life could not have arisen spontaneously in such an environment. Yet we and the majority of life on the planet cannot live without it. How ‘on earth’ did this paradoxical situation arise?
It is generally accepted by earth scientists that the earth (and the other inner planets) was formed by the collection of the many planetesimals orbiting the sun in the inner regions of the solar nebula. The gases left in the nebula after the formation of the sun were driven off from this region to where it coalesced into the gas giants, probably by the solar wind and the magnetic field of the fast rotating sun . The planetesimals were generally too small to hold an atmosphere themselves, so the nascent earth started cool and without an atmosphere. It heated up due to the deposition of the gravitational energy of the in-fall and the radioactivity of the elements uranium, thorium and potassium. Over time this boiled out volcanically a gaseous atmosphere, probably one largely of nitrogen, carbon dioxide and water vapour. There would have been no significant free oxygen. At the present time there are some 500 active volcanoes around the world which add an estimated cubic mile of solid material to the surface each year; at this rate, between 3½ and 4½ million cubic miles of solids would have been added by volcanoes in the life-time of the earth, comparing well with the total volume of the continental crust --- and volcanism may have been greater in the early days. But it is the gases with which we are concerned here.
It is not known whether this original reducing atmosphere remained or whether there was some major astronomical event to start one again. Professor Cloud  has suggested that some 3½ million years ago the earth captured the moon, an event of such violence to destroy the previous atmosphere and start a new one. He based his hypothesis on geological evidence for much larger stromatolites  in the Pre-Cambrian, showing considerably greater tides than today’s. The tidal effects would have strongly heated the earth and in time caused the moon to recede to its present distance. Whatever the early history, we still have to explain the source of the oxygen atmosphere of today.
In the early reducing atmosphere, any life must have been confined to anaerobic bacteria and primitive single-celled organisms. They could only have operated by the biological process of fermentation, a much poorer source of energy than respiration. The first source of oxygen must therefore have come from the photo-dissociation of water vapour by ultraviolet light, of which there was a plentiful supply from the sun. Ozone would also be formed and would initially react at a high rate with surface rocks. Calculations  show that this accounts for the oxidation of sedimentary rocks on the continents and in the sea over geological time. However it could only lead to an atmospheric concentration of oxygen one thousandth of that today, because of a self-limiting mechanism, called the ‘Urey Effect’  , in which the ozone protects the water vapour below from dissociation.
This ozone would also offer some limited ultraviolet protection to life in water. The life could still not tolerate the UV at the surface, but at a few metres depth it would be safe. It is believed that this allowed some photosynthetic processes to evolve. This releases oxygen from water during the reduction of carbon dioxide into carbohydrate, employing visible light so not subject to the ‘Urey Effect’. The build up of the oxygen concentration would have been very slow at first due to the capture of oxygen elsewhere and the limited areas of shallow water; deeper waters would have had convection bringing the bacteria to near the surface where they were still vulnerable to ultraviolet.
A major step in the build-up came when the oxygen concentration rose to above one hundredth of that today. Then respiration was able to evolve and replace fermentation as the energy source; this offered 30 to 50 times the energy release per molecule, as noted by Pasteur 150 years earlier when studying wines. At this oxygen level, ultraviolet can only penetrate some 30 cm into the sea. The evolution of more complex and efficient biological systems allowed life to colonise the deeper seas. This major evolutionary event occurred at the beginning of the Palaeozoic, 600 million years ago. Before this there is only fossil evidence for primitive life. Within a few million years we have the multiplicity of fossils of the Cambrian, Trilobites etc.
This burgeoning of sea life continued to raise the oxygen level until, at about one tenth of the present level, the deeper ozone layer cut off the ultraviolet at the surface and allowed life to colonise the land in the late Silurian, some 400 million years ago. Forests appeared in the early Devonian, producing more oxygen.. The eventual levels may have exceeded the current level in the Carboniferous: such an excursion could have led to a reduction in carbon dioxide, reducing the greenhouse effect and causing the ice ages of the Permian, 200 million years ago.
Well, that is my story. It’s really about how you and I came to be. Without oxygen, we wouldn’t be here. But without us and all our precursors, nor would the oxygen atmosphere. Perhaps there is a hint that we shall not find intelligent life on the other planets of the solar system, as they do not have a similar atmosphere.
Peter R Wallis
 Fred Hoyle first published this idea, explaining the segregation between the dense inner planets and the outer gas-rich giants and also the reduction in the angular momentum of the sun. Back
 Prof Preston Cloud, University of California, Santa Barbara, 1969. Back
 Stromatolites are dome-shaped structures found only in the intertidal range. Back
 Lloyd V Berkner and Lauriston C Marshall, Texas, 1965. Back
 Dr Harold Urey published it in 1959. Back
A Merry Christmas
and a Happy 2005
to everyone of you
Like the rest of the world – barring exceptions – I am imbued with the Christmas spirit, and can hear the herald angels sing. I will not, therefore, echo warnings about what food we should or should not be consuming (“it’s only once a year”). Nor will I make any remark about drinking (“the odd half dozen glasses can’t cause any harm”). And I shall keep one of my chief concerns entirely to myself, namely the media’s unremitting references to the Nanny State. I shall not point out – it being Christmas – that their attitude testifies to their basic ignorance of science; that the very invention of the term “Nanny state” proves that there is no reply to sarcastic or ironic remarks; that, in fact, we ought to thank our lucky stars that a caring state makes information available for our potential benefit; and that the media ought to adopt a more responsible attitude in explaining the links between society, science, and survival. I shall refrain from mentioning that, in my view, the all-pervasive plugging of personal choice can be overdone. It is overdone, when the chooser is ignorant of the consequences of his choice.
As I promised, I shall not mention any of the above, but - Scrooge or not – shall wish you again
A Merry Christmas
and a Happy 2005
to everyone of you
Last updated 28-Jan-2018 contact