Wednesday 28 July 2021

Salt glands in extinct marine reptilian killing machines

A time traveller in  the late Jurassic and early Cretaceous, around 150 million years ago, would be wise to avoid the open sea, for there she would have encountered reptilian killing machines, thalattosuchians. These reptiles were 4-5 metres in length and belonged—just like modern crocodiles—to the Crocodylomorpha, a once diverse group of animals.

Palaeontologists have established the thalattosuchians had morphological features that can be linked to living in pelagic or oceanic environments. I will not dwell on those adaptations but concentrate on one which has been the subject of a recent paper from Argentina concerning a new specimen of Dakosaurus andiniensis.

When we wrote our monograph on salt glands in 1975, there had been no search for evidence of their presence in extinct reptiles. However, it seemed highly likely that they must have been there. As a result of what we wrote, in the late 1970s I had a very enjoyable day with the late Peter Whybrow (1942-2004) at the Natural History Museum in London. He wondered whether the obvious depressions in the skull of hadrosaurs—duck-billed dinosaurs—could have been salt glands. Although semi-aquatic herbivores, there was the possibility they could have been potassium secreting glands as in the Common Iguana of South America. We also took the opportunity to look at a range of extinct marine reptiles, including ones collected by Mary Anning, and I was able to see clear depressions in the skull indicative of the presence of nasal salt glands.

In recent years there has been considerable interest in the presence of salt glands in dinosaurs and their relation to the morphological adaptations associated with a presumed marine or brackish water habitat.

In Dakosaurus andiniensis the arrangement of the internal anatomy is such that the nasal glands drain through a ‘nostril’ on either side of the snout via the antorbital sinus. However, a new twist in the story was discovered—a rearward extension of the antorbital sinus to form a suborbital diverticulum. That diverticulum is interleaved between the muscles that operate the jaw. Therefore, it was argued, operation of those muscles could be used to compress the diverticulum and expel rapidly secretion from the nasal salt glands gathered there. An analogous clearing of the salt glands can be seen and heard in the Galapagos Marine Iguana which snorts to cast the concentrated salt solution from its nostrils to the four winds.

What seems to be unknown is their mode of reproduction. From the little I have read, crocodylomorphs were oviparous, with aquatic forms having to lay their eggs on land. If so then a mechanism to expel actively secretion from the salt glands makes sense in that it would prevent salt encrustation and potential blockage of the system caused by evaporation.

These and related studies on the thalattosuchians appear to show an evolutionary trend from forms that lived in fresh water to those completely at home in a fully marine environment. They are also interesting in that modern crocodilians, the only survivors of the crocodylomorphs, have no sign of a nasal salt gland. Instead, the Estuarine crocodile or Saltie to Australians, was found, thanks to the efforts of Gordon Grigg at the University of Queensland, to have salt glands in its tongue.

The authors of the paper on Dakosaurus andiniensis, from the Universidad Nacional de La Plata, make the point that the presence of what must be salt glands in their specimen suggests that the animals could have dealt with a variety of prey from fish (usually, I see, described as the prey), other reptiles, all of which would be relatively low in salt, to invertebrates like squid which have the osmotic concentration of salt water. A specimen of a species of thalattosuchian was discovered in Cambridgeshire with stomach contents that included cephalopod hooklets, fragment of belemnite rostrum and bones, possibly from a pterosaur, suggesting these animals eat anything they can get hold of. I wonder if somebody would like to sit down and calculate the likely weight of the salt glands of Dakosaurus or other thalattosuchians as a percentage of their body weight and then do some armchair physiology, taking known secretory rates of salt glands and food intake for a reptile of that size, in order to calculate whether the salt glands could have coped with a mainly vertebrate diet or one containing lots of osmoconforming invertebrates like squid and other cephalopods. The results would be interesting either way. In other words, we could indulge in physiological time travel.

Young, Brusatte, De Andrade, Desojo, Beatty, Steel, Fernández,
Sakamoto, Ruiz-Omeñaca, Schoch. 2012.
PLoS ONE, 7, e44985, doi:10.1371/journal.pone.0044985

Fernandez MS, Herrera Y. 2021. Active airflow of the paranasal sinuses in extinct crocodyliforms: Evidence from a natural cast of the thalattosuchian Dakosaurus andiniensis. Anatomical Record, 1–16. https:// 

Wednesday 21 July 2021

Tinned fish for the Australian Army canned; zoology and the exigencies of war

Don’t mention the war! Not this time an episode from Fawlty Towers but the implied message during the Marshall-Serventy-Drysdale expedition around Australia in 1958. Despite having only one arm, ‘Jock’ Marshall had a distinguished record in the Second World War, leading a patrol behind Japanese lines in the New Guinea campaign. And he was clearly intent on winding up his great friend from Perth, Dom Serventy, on what he did for the war effort. Serventy, after a first degree from Western Australia, had acquired a Cambridge PhD with Frank Armitage Potts (1882-1937)—the ‘P’ in the famous book on invertebrates, BEPS, or as intoned in full, Borradaile, Eastham, Potts and Saunders. He then returned to Western Australia as a lecturer but in 1937 joined the fisheries division of CSIRO. And it was while working in fisheries that he became a hate figure to the Australian army. In Marshall’s words, the subject was raised one night during the airing of Ivan Carnaby’s ‘unsolicited views on army life and the evils thereof’. In Marshall’s words:

It was at this camp that we got some understanding of an affair that had been bothering some of us for several years past. Looking at Dom's face—a face benign in repose as he contemplatively swigged at a pannikin of rum and water in his swag near the fire—it was difficult to believe that here was one of the men most detested in the Pacific Theatre during the war against the Japanese. There was little about him now that would suggest that Dom was one of a group of persons whom many people wanted to indict as war criminals. Generally, if one is unfortunate enough to find oneself in the company of such a person, one tends to avoid like a plague the subject of former contention. But we had heard so many conflicting stories about the part that Dom had played in this unsavoury business that we felt that this would be a good opportunity to let him talk about it and, if he chose, to offer an explanation to us, an essentially sympathetic audience.
So in our tactful way we said suddenly, ‘Tell us about your part in that rather disagreeable goldfish business during the war, Dom.’
There was silence, except for the crackling of the fire. Ivan, a close friend of Dom's, and once a soldier, stirred uneasily.
‘It was not goldfish,' said Dom quietly. ‘The fish is
Nematalosa erebiya so-called bony bream. It is, in fact, a true herring—one of the soft-rayed clupeoid fishes. It is a Perth fish, and therefore a good fish.'
There was another silence.
‘It is true,' Dom started off again, ‘that it does not command any sale when fresh. But is nevertheless a very fine fish, and it can be caught easily in great numbers by means of mesh nets of the beach seine type in the Swan River, the Leschenault Estuary and elsewhere. Leschenault was one of Peron's men in Baudin's expedition of 1801.' 

‘It would be rather pleasant if you didn't change the subject,' somebody said. 

‘Well,' resumed Dom, with some dignity, ‘in World War II, Mr A. J. Fraser, Director of Fisheries, whom you have met, suggested to Mr Vincent Gardiner, whom you do not know, that as he was already engaged in the production of turtle soup, it might be extremely helpful to the war effort if he, Mr Gardiner, experimented with the canning of certain common Western Aus­tralian estuarine fishes, particularly Perth herring, for which there was no demand when fresh. It turned out to be a very good product,' concluded Dom, a little defiantly. 

‘But how did you get mixed up in these criminal activities?’ somebody broke in. 

‘I was transferred home to Western Australia during the war to work on, among other things, the biology of the Perth herring, ‘It turned out to be a very fine fish. Not perhaps of the quality of good Scotch salmon, but nevertheless, a very good fish and, in tomato sauce, very similar to European herring.
‘It is true, unfortunately, that the flesh is comparatively soft. Therefore it does not stand excessive handling during transport. When tins of Perth herring eventually reached the forward troops the fish was still tasty, but appearances were against it. 

‘Irrationally, the privates objected.’
‘Various personages associated with this delectable product, notably A. J. Fraser, Vincent Gardiner and myself went in some danger of our lives.’ 

‘It was even suggested that we be arraigned before the war criminal courts on charges of having conspired with the Japanese to lower morale.’

‘This charge is not true.’
There was silence except for the crackling of the campfire.
‘It was an attractive product, I thought,’ said Dom.
‘I enjoyed them.’
‘It was an honest attempt urgently to step up production of a food in short supply.’
‘How were we to know they wouldn't travel?’
‘We did our best.’
‘I would accept a tin of this fine Perth fish any time.’

I think we can take it that Jock Marshall, deep in the tropical jungle of northern New Guinea, was perhaps not terribly impressed by the odour, flavour or consistency of a disintegrating detritus-feeding fish in tomato sauce.

Perhaps then not surprising that Serventy moved to the wildlife division where he could pursue his lifelong interest in birds.

Perth Herring

The fish in question is now known as Nematalosa vlaminghi and it goes under the common names of Perth Herring, Bony Bream (but not to be confused with N. erebiya also known by that name) and Western Australian Gizzard Shad. It spends a period feeding at sea and then migrates to spawn in estuaries. Vincent Gardiner had a factory, Ocean Canning Company, at Belmont, Perth. Born in Dorking, Surrey in 1893 and educated at Reigate Grammar School, he began his career at sea as a radio operator. He then became superintendent of the Marconi School of Wireless in Sydney. A move as sales manager of Amalgamated Wireless also in Sydney was followed by his starting a gasket and felt company in Brisbane and Sydney. In 1937 he moved to Perth and began a meat canning company. It was there that he met A.J. Fraser and, as explained by Serventy, set up a canning factory for Perth Herring. The Australian army contracted to buy his entire output.

Although Gardiner moved into other lines, he was continuing to can Perth Herring for the civilian market into the 1950s. The tins were sold in Western Australia under the ‘Seahaven’ brand but production was insufficient to market them elsewhere. In a brochure extolling the virtues of Belmont, a former factory worker recalled his time working for Gardiner from 1940:

My original job involved cleaning fish, these being Perth Herring. The local fishermen received one penny per pound for them and cleaning was usually done by women who were also paid one penny per pound.

I wonder how Perth Herring in tomato sauce compared with my weekly lunch of sardines on toast or that dish still popular with Brits of a certain age, tinned pilchards?

Marshall AJ, Drysdale R. 1962. Journey among Men. London: Hodder & Stoughton. Paperback: Melbourne: Sun Books 1996 (reprinted 1967 (twice), 1968).

Monday 12 July 2021

JOURNEY AMONG MEN by Jock Marshall and Russell Drysdale. A zoological/nuclear fallout expedition around Australia in 1958

Although I have written about him in previous articles on this site, have read some of his papers, have seen some of the press cutting about him and been in his first lieutenant’s department for a while, I had not read any of Alan John ‘Jock’ Marshall’s (1911-1967) books. The first to arrive was Journey Among Men, first published in 1962. I was pleased it was the first since I was intrigued by what the collecting expedition, which covered much of western and southern Australia it describes, was all about. I was also interested in his description of places we had been to in the Kimberley region of Western Australia 60 years later.

The real reason for the expedition was only alluded to in the book and I will return to the background later. Much greater emphasis is placed on the people, places, animals and plants encountered while travelling the vast distances and camping most nights. The book itself is an extended compilation of articles Marshall wrote for a Sunday newspaper, The Observer. Writing was completed when Marshall had moved back to Australia—to the then new Monash University in Melbourne, from London. The expedition though started in September 1958 when he was still Reader in charge of the Department of Zoology at St Bartholomew’s Hospital medical school.

The route of the expedition. The first party started at Perth and the second in Sydney.
They met at Fitzroy Crossing in the Kimberley region of Western Australia

The members of the expedition were, apart from Marshall himself:

Dominic Louis Serventy (1904-1988), an outstanding ornithologist, at that time in the wildlife survey section of the Commonwealth Scientific and Industrial Research Organisation in Perth. He collaborated with Marshall in research on the breeding cycles of birds and he, with Marshall, began planning the expedition in 1957.

Kenneth Gordon Buller (1915-1995), collector, ornithologist and taxidermist. Buller was senior preparator at the Western Australian Museum. He returned to Perth after the survey of Montebello and Barrow islands.

They, with Marshall, set out from Perth on 11 September in Serventy’s Land Rover and trailer. 310 miles north at Yalgoo they were joined by:

Ivan Clarence Carnaby (1908-1974), farmer, naturalist and another noted ornithologist; he travelled in a battered Dodge ‘ute’ which Marshall, avoiding the Australian slang, spelt out in full as ‘utility vehicle’. He didn’t though go the full British and call it a pick-up. He returned home before the run south from near Port Hedland. Disliked ‘graduates, Yanks, bot-flies, snakes and Eastern Staters’.

That was the Western party. After working their way up, doing what they had to do on the way, they were to meet the Eastern party at Fitzroy Crossing, over 1,500 miles from Perth, in the Kimberley. The Easter party comprised:

Russell (Sir Russell from 1969) ‘Tass’ Drysdale (1912-1981). Artist and friend of Marshall. He added an account of the travels from Sydney, through New South Wales, Queensland and Northern Territories to Fitzroy Crossing as well as providing drawings of the people met on the journey among men; the drawings illustrated the articles for The Observer, as well as the book. With him was his son:

Tim Drysdale, employed by Marshall as a helper to the expedition.

Jane Marshall described the circumstances:

It was on this journey that Jock and Tass discovered the depth of their friendship. It was in part due to the troubles of Tass's son Tim, whom Jock was employing for the rest of the trip as mechanic and general helper. He had deep compassion for the sense of helplessness and sadness Tass felt in not being able to reach his son emotionally or guide him out of his difficulties.

The Drysdale story did not end well: Tim Drysdale killed himself in 1962, the year the book was published; his mother followed a year later.

A fly-in, fly-out member of the expedition was Donald Sankey Farner (1915-1988). He was then Washington State University at Pullman but in 1958 he was spending a year in Perth on a Guggenheim Fellowship working with Serventy on the control of the reproductive cycle in the Zebra Finch. He was one of the key players—along with his friend Marshall—in lifting ornithology from its traditional descriptive focus to a broader base including how birds work. Thus his ‘avian biology’ has a very different connotation compared to ‘ornithology’. Don Farner—the only member of Marshall’s expedition I knew or met—arrived by air near Fitzroy Crossing and left, from my reckoning of he description of the book from Marble Bar airport near the start of the road south that leads south to Kalgoorlie. Farner came into a great deal of ribbing by the Australians because he always used pills to sterilise his drinking water—and doubled their number when dead pigeons were found in a water tank from which they had filled their bottles.

No member of the expedition travelled the whole distance. Russell and Tim Drysdale travelled the longest distance, starting and finishing at Sydney.

Why the expedition?

The 1950s was everything nuclear: from nuclear power and nuclear weapons to nuclear medicine and the use of radioactive isotopes in biological research. The intended research of the expedition seems to have depended on three strands: (i) Marshall’s own interest in the factors controlling seasonal reproduction; (ii) Marshall’s befriending of Joseph Rotblat at Barts Medical School, (iii) reports of the appearance in Kenya and Britain of some migratory birds in nuptial rather than eclipse plumage; the birds that had arrived in Britain were found to contain radioactive isotopes from nuclear weapons tests.

The whole story about plumage and radioactivity is told in the 12th Annual Report of the Wildfowl Trust for 1959-60 in an article by JM and RG Harrison:

The first suggestion that birds were being affected by radioactive fallout was made by Mr. John Williams, Ornithologist to the Coryndon Museum, Nairobi, who wrote to The Times in December 1955 stating that certain wading birds had appeared that autumn in Kenya in what appeared to be fresh summer plumage, the species in question being Greenshank and Sanderling. He commented that “It makes one wonder if these birds have been in a radioactive area in northern Russia, which has somehow affected their moulting sequences.”

On 9th November of that same autumn we had collected a female Redshank of the Icelandic race on the Medway Estuary in Kent (Harrison and Harrison 1956a), which was already in advanced freshly-moulted summer plumage, the breast and flanks being heavily spotted and streaked and the back, the head and neck showing the black streaks and barring of summer, the whole plumage being strikingly different from another female in normal winter plumage, which was shot on the same day. It is well known that some gonadal recrudescence occurs in autumn and this is responsible for autumn song and courtship, in such species as the Chaffinch, Song-Thrush, Dunlin, Redshank and Mallard, but we could not trace any record of a wading bird actually assuming summer plumage.

Following the exhibition of the Icelandic Redshank at a meeting of the British Ornithologists’ Club, consequent upon Mr. Williams’ remarks in The Times, arrangements were made with Dr. John Loutit of the Radio­biological Research Unit of the Atomic Research Establishment at Harwell for the examination of the bones of any further birds suspected of radioactive contamination. On 24th December, 1955 a further Redshank (Harrison and Harrison, 1956b) was obtained at Rye Harbour which showed incipient summer plumage and on dissection the ovary and oviduct were more fully developed than is normal in individuals collected at that time of year. Part of the skeleton was therefore sent to Harwell where it was dissolved in nitric acid and the presence of radioactive contamination was confirmed by Dr. G. E. Harrison and Mr. W. Raymond using a Veall Geiger Counter, and a graph prepared of the decay of the skeletal activity over the next two weeks. Dr. Loutit’s report stated that “ at least it proves that the bird had been exposed to some radiation,” but he went on to add that of course in a series of one there is no control. The ovary and oviduct were submitted to Dr. A. J. Marshall who reported that “the slides show quite clearly that the bird has become sexually advanced. You will see that the oocyte diameter (in the largest cases) is somewhat in excess of what would be expected for an ordinary wintering bird. This probably connotes oestrogen liberation. The oviducal proliferation is of course a consequence of oestrogen liberation.”

Dr. Loutit thought that the effect, although it appeared like a stimulatory action of radiation, was more likely to have resulted from an initial depression and a subsequent rebound phenomenon; the radiation first depressing cellular activity and thus delaying the assumption of summer plumage, and then as the effect wears off, the bird going into breeding plumage as a late phenomenon and out of its proper season.

So that is how Marshall became involved. Clearly though he was talking to his opposite number in the Physics department, Joseph Rotblat (1908-2005). According to Rotblat’s biographical memorialists for the Royal Society, for a time after his appointment to Barts the only person who would talk to him was Marshall. I cannot deduce whether this was because of Rotblat’s controversial past in the development and then repudiation of nuclear weapons or because he was not medically qualified; either or both could be the case. At this time Rotblat (later Sir Joseph and winner of a Nobel peace prize) was working on the biological effects of radiation and it is easy to envisage he and Marshall cooking up a scheme to study the effects of radiation on reproduction in birds.

The studies were funded by the Nuffield Foundation and, as explained in a news snippet in New Scientist (23 October 1958) the approach was two-pronged:

Suspecting that radiation may have upset the sexual cycle, Dr. Marshall is to collect several hundred fish, amphibians, reptiles, birds and mammals in different parts of Australia exposed to different amounts of radioactive fallout. A colleague, Dr. Brian Lofts, will carry out laboratory experiments on African weaver-finches, chosen for their periodic plumage changes.

The sites with the most exposure to radioactivity were of course those used for the British atomic weapons tests in the 1950s: Trimouille and Alpha islands in the Montebello archipelago off north-western Australia (1952 and 1956); Maralinga (1956, 1957) in South Australia. The visit to Montebello hardly gets a mention in the book, other than: ‘And on one of the Monte Bellos, a whole hillside, scorched by the incredible blow-lamp of an atomic bomb, testified to the most recent visitation by man’. There is a little more information in Jane Marshall’s write-up of her husband’s biographical notes:

Jock had a geiger counter and on Trimouille Island went ahead 'a little wary of the bay in which the guineapig ship was blown up in the first explosion.' They found the whole cliff-face scorched by that 'incredible blow-lamp of the atom bomb', then came to the slightly radio-active huts in the probable fall-out area as mapped for them by the people at Aldermaston in England, who were extremely interested in the investigation. There was not much more radiation than given off by Jock's watch until they came to what was probably wreckage from the ship. This was very active. 'We collected 42 terrestrial vertebrates on the islands, retaining the skins for the W.A. Museum & preserving the bodies for analysis at Bart’s.'


On the way [to the Kimberley] they were collecting vertebrates in an arc around the Monte Bello area for shipment to London.

By the time the expedition came to Maralinga, there were only three members left: Marshall and the two Drysdales. Again, the work there was passed over in two sentences: ‘The work on which we were engaged at Maralinga has no place in this story. We spent some time at the base where we slept in sheets, went to motion pictures whenever we wanted to, ate ridiculously good food and used base facilities to overhaul the truck’.

Jane Marshall expanded thus:

Maralinga was Jock's most important goal. They arrived on October 28th and found 'a swimming pool, a change of picture show every night, tennis courts & superb cooking in the Commander's mess, where I am.' He found he had met the Commander and Chief Administration Officer during the war. This was another world from the one where they carried their water and selected their camps according to the firewood supply. Issued with protective clothing and placed in the charge of a security officer Jock went about collecting '313 terrestrial vertebrates in specifically "dirty" areas and in “clean" areas nearby. As before these included mammals reptiles and ground birds ... Of the Maralinga material some reptiles showed a count significantly higher than that of the background.' 


I have searched without success for reports on the results of monitoring animals for radioactivity. Was this because nothing of interest was found or because, which must have been the case in Maralinga, security clearance must have been obtained and the results treated as confidential? Grantees write reports on how they had spent their funds (I have one John Phillips wrote to the Nuffield Foundation on his funding for comparative endocrinology in Hong Kong) and I wonder if there is anything in the Nuffield Foundation’s archives. Jane Marshall mentioned that Aldermaston (Atomic Weapons Research Establishment) was interested in the results. Was a report sent there?

By contrast, two papers were published by Brian Lofts (1929-2015) and Joseph Rotblat on the direct, experimental approach to studying the effects of radiation on birds. Effects on the testis and on the regeneration of feathers after exposing Red-billed Queleas (Quelea quelea) to x-rays were found. While the results were interpreted as suggesting that irradiation had upset the pituitary cycle which controls the onset and loss of breeding plumage—as originally proposed for the appearance of birds in breeding plumage in Kenya and England after migration—the results were not followed up and several interpretations are possible for the appearance of a black band in the regenerated feathers of irradiated female queleas.

I suspect that little was achieved by Marshall’s expedition in relation to its original purpose. However, it is clear that the opportunity was taken to survey the wildlife in Western Australia and I have found that a CSIRO report was written by Serventy and Marshall: A natural history reconnaissance of Barrow and Montebello Islands 1958. Farner also clearly, as described in the book, took the opportunity to extend his work with Serventy on the control of the breeding cycle in the Zebra Finch.

Jock Marshall also spent time in Australia scouting out potential jobs for a return there from London. He, in the ultra-conservative world of Australian universities, and a self-confessed former larrikin was considered rumbustious and, as I explained in an earlier article, had acquired an influential sworn enemy as a result of the Golgi War. Eventually though he was offered a chair in the new Monash University and it was there that the book was written. How the people of Adelaide and Melbourne—the ‘wowsers’—greeted Marshall’s definition of the term (‘a gentleman who uses a contraceptive as a book-mark for his Bible’) greeted his return—or the book— is not recorded.

Journey among Men

The Marshall-Drysdale book is a fascinating account of life in the outback in the 1950s through the eyes of a thinking Australian zoologist who had spent many years in Oxford and London. To have followed in the expedition’s footsteps 60 years later at Winjana Gorge, Tunnel Creek, Hall’s Creek, Fitzroy Crossing, Geikie Gorge, Derby and Broome was equally interesting. For some places like Geikie Gorge and Tunnel Creek Marshall’s description still fits; for others like Broome, the place and people have changed beyond all recognition. Well almost, because visitors, even poms, will come across some old boy with a tale to tell. But the days must have gone when a notice could be seen on the pub wall in Port Hedland:

Whispering Smith has taken out an order restraining Billy the Lurk from drinking intoxicating liquor for a period of three months.


The following are a few of Drysdale's illustrations for the book:

This is the poignant back cover of the 1968
paperback edition of Journey among Men

A view in the Kimberley, 2018

Marshall AJ, Drysdale R. 1962. Journey among Men. London: Hodder & Stoughton. Paperback: Melbourne: Sun Books 1996 (reprinted 1967 (twice), 1968.

Marshall Jane. 1998. Jock Marshall: One Armed Warrior, Australian Science Archives Project, Melbourne.

Harrison JM, Harrison JG. 1961. Radioactive contamination in birds. Tweflth Annual Report of the Wildfowl Trust 1959-1960, 151-152.

Hinde RA, Finney JL. 2007. Joseph (Józef) Rotblat. 4 November 1908 — 31 August 2005. Biographical Memoirs of Fellows of the Royal Society 53, 311-326.

Lofts B, Rotblat J. 1960. Effects of wholebody irradiation on the breeding plumage of the weaver finch, Quelea quelea. Nature 187, 615-616.

Lofts B, Rotblat J. 1962. The effects of whole-body irradiation on the reproductive rhythm of the avian testis. International Journal of Radiation Biology and Related Studies in Physics, Chemistry and Medicine 4, 217-230.