© 1976 by Thomas Donaldson, Ph.D.
[Note: This article was written in 1976 and converted to electronic form by Robert Bradbury in 1999. It contains many interesting ideas and observations that remain valid to this day. Nevertheless, it is outdated in some respects. In particular, our understanding of how memory works is now somewhat different. For further information see discussions of LTP, Memory and Neural Activity and the Bibliography on Memory at PERIASTRON.]
We can begin with some definitions. Cryonics is the practice of frozen storage of human beings, if necessary, for hundreds of years, until they can be revived and cured of whatever illness or injury caused their legal death. Cryonic suspension is the procedure by which a patient is frozen after legal death.
Some other definitions may also help to understand the practice of cryonics. Legal death is the condition of someone who has been pronounced "dead" by an authority legally qualified to do so. Legal death is a legal and not a biological state. Usually the notion of "death" involves ideas that anyone who is "dead" can never return to life. We will argue here that almost all cases in which people are commonly pronounced "dead" will someday become reversible, treatable conditions. To prevent confusions, therefore, it may help to have a special word for these states. Deanimation is the state in which a person (or animal) no longer shows any of the signs such as heartbeat or brain activity normally associated with life: it as if they have been turned off‘ and stopped working in the same way a phonograph is turned off and stops working. We shall argue in this introduction that almost all cases of legal death are actually different types of this condition of deanimation. However, unlike "death", deanimation carries no implication of irreversibility or finality to it at all.
Immediately when the possibility of cryonics is raised, all kinds of questions come to mind. Why do we want to do such a thing to ourselves or others? What could someone hope to gain by it Why do we think that we can be stored for so long? What is the chance that we will really come back?
This introduction will give answers to these questions.
AGING AND "IMMORTALITY"
I do not wish to belabor this point, which is nevertheless the MOTIVATION for cryonics. It is not proposed to bring back old people only for them to die soon afterwards. It is proposed to keep them frozen until their aging can be significantly REVERSED. Control of growth and development will serve adequately to accomplish this. One excellent short popular article discussing this possibility, which seems far closer than most people think, is:
A. Rosenfeld, The death of old age, TIME-LIFE NATURE-SCIENCE ANNUAL (1975)
At this point it is useful to explicate what would be meant by "immortality" in our terms. Through history the character of those diseases which afflicted people has changed. Many primitive populations show low death rates from cardiovascular diseases: this stems from the fact that few live long enough to develop such problems. I DO NOT BELIEVE THAT THERE WILL EVER COME A TIME IN WHICH WE CAN EXPECT TO LIVE INDEFINITELY WITH NO FURTHER CHANCE OF DESTRUCTION. [Editor's Note 1] Means to raise lifespan to 400 years may very well come quite soon. Yet there will be still more diseases which do not appear now because no one lives long enough to suffer from them. lt is foolish to expect that we can hope to live indefinitely without taking active steps to acquire this life. No discovery in gerontology is even remotely probable that will give us longevity without subsequent effort.
HOWEVER the combination of gerontology PLUS freezing PLUS vigorous research into means to eliminate all possible fatalities is VERY POWERFUL, and likely to lead to a state not far indistinguishable from "immortality" itself. It would mean that virtually any time YOUR BODY IS FOUND, you can be frozen and hope at some time to be revived. It is only possible to make rough calculations of how long you might expect to live under these conditions. However, complete elimination of aging would imply an average lifespan of about 600 years. Even in most cases of accidental death, the body is recoverable very soon afterwards. A rough estimate of the length of time someone may expect to live before his body is totally destroyed by accident is about 100,000 years. Vigorous attempts to reduce the number of destructive accidents will probably reduce the rate very much, leading to corresponding increases. A reduction of the accident to 1/10 its present value, for instance, would imply, on these figures, an average longevity of 1,000,000 years.
SOME TECHNIQUES OF REPAIR LIKELY TO BE AVAILABLE
I do not think that repair would be anything so crude as cloning. It seems to me what is most likely is that a new body would be reconstructed from the old.
I. REPAIR AT THE LEVEL OF THE CELL
II. REPAIR AT THE LEVEL OF THE WHOLE ORGANISM
There is a voluminous literature on freezing which I will not summarize. A good survey article is:
Robertson, R. D., Jacob, S. N. "The preservation of intact organs" in Advances in Surgery 3. Welch, C., (ed.) (1968)
Present work on freezing continues. The U.S. NIH is funding a study of kidney freezing at the U. of Minnesota. A reader may consult the journal CRYOBIOLOGY or SURGERY for reports of this work.
I have collected together a number of studies of freezing of tissues and organs. Some facts about freezing are relevant in evaluating these reports. At temperatures higher than –196°C, recrystallization of ice occurs slowly over a period of days, causing damage. Temperatures above –130°C are not optimal for long-term preservation. On the other hand, the present consensus of cryobiologists is that most damage in freezing and thawing occurs at the range of –78°C and above. This consensus may help to motivate the fact that so much work has been done on freezing and thawing organs from such (relatively) high temperatures. A second fact to remember is the existence of cryoprotective agents. These prevent or mitigate the damage of freezing. Two particularly effective agents are DMSO and glycerol.
||1 mm tissue slices taken from human cadavers, stored
in LN2 for months. All showed growth in culture after thawing.
Tissues studied were: ovaries, testes, pituitary, thymus, adrenals, liver,
thyroid, parathyroid, pancreas, kidney, intestine. No brain tissue studied.
Perry, V. P., Fed. Proc. 22:182 (1963.)
||Whole rabbit kidneys frozen in LN, without cryoprotective
agents. Kidney epithelium grew in culture after thawing.
Klinke, J., Growth 3:169 (1963)
||Whole dog kidneys, perfused with DMSO, stored for
one year. Cell cultures taken from the thawed kidney immediately after thawing.
Growth in culture of all cell types the same as that of controls.
Robertson, R. S., Jacobs, S. N., op. cit., p.145)
||Kidneys perfused and cooled to –50°C. DMSO used.
Of 37 kidneys treated, 4 supported life long-term in dog after other kidney
Halasz, Surgery 61(3):417-21 (1967)
||DMSO used, 2 of 14 kidneys functioned long-term.
Mundth E. D., Cryobiology 2(2):62-7 (1965)
|Some observations about work on kidneys are worth making. Quite frequently frozen kidneys will function for a short time after thawing. Degeneration occurs later, over a period of days. lt seems to me that this is excellent ground to believe that repair will be possible in future, even if it is not possible now. Our problem is to find a way to prevent this degeneration, not simply to revive the kidney in the first place.|
||Brains perfused with glycerol and stored at –90°C
show no return of electrical activity. Few details of time or storage or
Suda, I., Brain Research 70(3):527-31 (1974)
||Cat brains, perfused with glycerol and stored for
280 days at -20°C recover electrocortical activity upon rewarming to 39°C
and perfusion with fresh donor blood. Techniques of freezing much more
crude than those of studies on kidneys. Appearance of tissues in light
microscope "almost normal" (original reference contains photograph).
Suda, I., Kito, K., Adachi, C., Nature212(59):268-70 (1966)
||Cat brain stored for 7.25 years, thawed slowly
over 12 hours. Brains perfused with glycerol before freezing. Spontaneous
electrical activity from thalamus and cerebrum.
Suda, I., Brain Research 70(3):527-31 (1974)
The arguments for irreversibility of this so-called "death‘ are CIRCULAR and rest on no scientific grounds whatever. The only support for belief in irreversibility consists of the universal UNEXAMINED belief in it.
It is not possible to argue this question of irreversibility in the terms in which it is usually asked. At present, for most injuries and diseases, the custom is to take those who are afflicted with them, put them in boxes, and bury them. When, because of this treatment, they decline still more until they become dry bones, these dry bones are then exhibited as evidence for the irreversibility of death and the folly of believing that dead people might ever be restored to life. It is one point of cryonics that WE DO NOT INTEND TO ALLOW MATTERS TO GO THAT FAR.
As a general strategy, we systematically attempt to preserve as much as possible. EVERYTHING THAT REMAINS GIVES US MORE TO BUILD ON FOR FUTURE REPAIR. This strategy involves trying to get people as soon as possible. Given present conditions, this may be hours or even days. Even if we cannot perfuse and freeze someone immediately, we CAN do one thing, which is to refrigerate them. By lowering their temperature to 0°C we can slow down all the chemical reactions involved in their deterioration.
In the absence of knowledge of how memories are stored in the brain and therefore of concrete signs of persistence or lack of persistence of identity, we must rely on indirect evidence about the general state of the cells when subjected to various treatments after deanimation of a patient. To give this discussion some empirical content, I have collected together here some information about the state of cells of various types, after remaining at various temperatures, mainly 37°C and 0°C (temperature of refrigeration). Naturally the cells in question are kept at these temperatures without oxygen or nutrients.
The general character of these experiments will be well known to biologists. It has been known for a long time that signs of life persist for hours after "death" has been legally declared. THE SIGNIFICANCE OF THESE FACTS, HOWEVER, SHOULD BE REEVALUATED.
FURTHERMORE, IT SHOULD BE POINTED OUT that there is right now very intensive research going on directed specifically to finding ways to revive the "clinically dead". Some of this work is described in the table below. The status of being "dead" by present criteria has virtually the same scientific status as that of suffering from acute multiple sclerosis. You will not last long; nonetheless there is very much scientific research directed at the problem, and a general belief that a cure will eventually be possible.
||COMMONLY ACCEPTED TIME LIMIT AFTER WHICH REVIVAL IS IMPOSSIBLE|
||Adult monkeys survive long-term with no neurological
deficit when in addition to customary measures of resuscitation they are
also given special drugs. 100% survive this treatment: drugs are given AFTER
the period in which circulation to the brain has been cut off for 16 min
at normal body temperature.
Bleyaert, A. L., et al., Crit. Care Med. 4(2):130 (1976)
||Rat brains kept at 37°C. Using hematoxylin and
eosin stains, no abnormalities in cell structure earlier than 38 min. Neurons
with swollen mitochondria will be seen in many parts of the brain.
Becker, H., Amer. J. Path. 38:507 (1961)
||Swelling of mitochondria and discontinuities of
cell membranes of cat retinal neurons at 40 min without oxygen in
vitro at 37°C. All changes will reverse when oxygen is restored.
Webster, N.D., Ames, A., J. Cell Biol. 26:885 (1965)
||Monkey and cat brains, deprived of circulation
for a period of 1 hr, will recover normal electrical activity and show continued
normalization of all other functions for a period of 48 hours. (At present
experimental preparation cannot be maintained past that time). Animals given
noradrenalin and other drugs after the period of ischemia to promote revival.
Both light and electron microscopic studies of brains immediately after
1 hr's ischemia shows no abnormalities.
Hossmann, K. A., Sato, S., Science 168:375 (1970);
Hossmann, K. A., Kleihues, P., Arch. Neurol. 29(6):375-84 (1973)
||Brain slices kept for 2 hrs in Krebs-Ringer solution
without oxygen at 37°C show no measurable loss of either RNA or DNA.
Becker, N., Amer. J. Path. 38:587 (1961)
||Rabbit cerebellum kept for 4 hrs at room temperature
(25°C). Enzyme activities studied using special microscopic stains. Acid
phosphatase (lysosomal enzyme), glucose–6–phosphate dehydrogenase
(enzyme of glucose metabolism), others studied. Location in cell of
all enzymes studied remains the same.
Lazarus, S. S. et al., J. Neurochem. 9:227 (1962)
||Lyzosomal acid phosphatase studied in brain
tissue incubated without oxygen or nutrients for periods from 2 to 72 hrs.
Enzyme can be distinguished as: "free" = enzyme outside lyzosomes. Control
rat brains had 30% free activity. After 1 hr of incubation free activity
rises to 32%; at 6 hrs it has risen to 45%. Under light microscope with
stains for acid phosphatase, no change in location of enzyme can be seen
up to 6 hrs. After (but not before) 6 hrs it tends to concentrate around
Anderson, P. J., J. Neurochem. 12(11):919-25 (1965)
||Brains of adult dogs studied postmortem. Dogs kept
at room temperature, cells studied under light microscope using stains luxol
fast blue and cresyl echt violet. Progressive agglutination and fragmentation
of Nissl substance begins about 6 hrs: Nissl substance disappears by 24
hrs. From 6 to 24 hrs nuclear and cell membranes become progressively irregular
and there is an increase in vacuolation.
Haines, D. E., J. Comp. Neurol. 132(3):405-17 (1968)
|LIVER||For comparison with brain, I include some data on cell changes in livers deprived of oxygen and nutrients.|
||Rat liver tissue in vivo. With lack of oxygen mitochondria
swell, endoplasmic reticulum becomes fragmented and dilated, vacuoles form,
other changes. All changes will reverse to give a normal appearance if the
duration of deprivation is not more than 68 min.
Bassi, M., et al., Exp. Molec. Path., 31:332 (1964)
||Mouse liver, removed from mouse and incubated.
Control livers had 42% acid phosphatase free; 67.8% free acid phosphatase
at 68 min; 82% free at 120 min.
van Lancker, J. L., Amer. J. Path. 35:563 (1959)
||Dog liver may have circulation cut off for 30 min
Goodrich, E. O., Surgery 39:244 (1956)
||Adult rats recover after 2 hrs of complete circulatory
arrest and arrest of lung ventilation at 0°C.
Andjus, R. N., Physiology 128:547 (1955)
||Puppies kept at 10°C to 12°C for periods of 2.5
hrs with circulation arrested. Lungs ventilated artificially despite circulatory
arrest. 6 out of 6 chronic survivors, 1 with moderate brain damage, 5 with
no persistent disorders.
Kondo, Y. et al., Cryobiology 11(5):446-51 (1974)
||Hamsters recover after 4 hrs of cardiac and respiratory
arrest at 0°C.
Huggins, C. E., Surg. Forum 12:413 (1961)
||Whole dog brains, removed from dog and perfused
with Ringer solution, and stored in refrigerator for 4 hrs, recover normal
electrical and metabolic activity on rewarming and perfusion with donor
blood at 34°C. Electrical activity of brains at 12 and 18 hrs not tested
in this experiment.
White R. J., Nature 209(30):1320-2 (1966)
||Infant ground squirrels survive supercooling to
-8°C for 5 hrs.
Infant ground squirrels survive supercooling to -4°C for 11 hrs.
Popovic, V. P., and Popovic, S. Amer. J. Physiol. 204:949 (1963)
|12 to 24 hrs||Tissues removed from human cadavers and stored
at 4°C for periods up to 24 hrs. Cultures in vitro will show cellular growth
and multiplication. No differences in viability depending on the time of
storage from 12 to 24 hrs observed; brain or nervous tissue NOT tested.
Perry, V. P., Fed. Proc. 22:102 (1963)
||Dog kidneys preserved for transplants. Initial
perfusion with special solution, storage in ice for 3 days, viable on transplantation.
Sacks, S., Petritsch, P., Kaufman, J., Lancet 1:1024-8 (1973)
||Reflex eye movements of leopard frogs remain good
for 3 days.
Sollmann, J., Amer J. Physiol. 149:299 (1947)
||Human embryonic lung cells. More than 50% viable
after storage at 4°C for 3 days.
Matsumura, T., Exp. Cell Res. 76(2):297-304 (1973)
||Dogs brains, removed from dog, perfused, and stored
in refrigerator for 15 days at 2°C, will show 50X of respiratory activity
of normal brains or brains stored for 12 hrs or less. No change in measure
of respiration between 18 hrs and 15 days. Cell structure of brain tissue
examined with hematoxylin and eosin stains and found to be normal.
White, R. J. loc. cit.
SURVIVAL OF IDENTITY
It is a very good question to ask of cryonics exactly what evidence do we have that personality or identity survives after "death"? Since we do not yet know what structures encode our personalities, we cannot yet prove that they survive.
The current best theory as to memory encoding says that it is encoded in the pattern of connections between our neurons, particularly in our brain cortex and cerebellum. A great deal of research on just this question has occurred since 1975, when the first issue of this Bibliography was distributed. [Editor's Note 3 ] Rather than explain in detail just what might happen to memory during and after freezing I will refer to a second discursive bibliography, distributed at the 1997 Alcor Cryonics Conference in Scottsdale, AZ (I can provide this bibliography upon request).
T. Donaldson, Brief Bibliography on Brain Preservation and Repair (1997); Alcor Cryonics Conference 1997, Scottsdale. AZ
Some further interesting references are:
The primary paper here is the Hershkowitz paper. The salamander brains were simply placed in the brain cavity; they worked out how to rearrange themselves by themselves. This suggests that our own brains may retain a good deal of information about their proper structure including the memories they contained, even if we do not now know how to retrieve it. Yes, salamanders are not people. However current work on repairing human brains strongly suggests that our neurons retain much information also. The problem with human (and mammalian) brains comes not from lack of information but from frustration of repair by various other biochemical factors.
It is quite possible, and even to many cryonicists very likely, that cryonics will become widespread NOT when someone is actually revived, but when popular knowledge of our likely ability to recover memory become widespread. For the preservation of memory tells us whether or not revival is possible in PRINCIPLE, rather than merely in PRACTICE, and anyone can see that practice is of all things the most temporary.
However, even here there is a minimum of ignorance which no amount of scientific work on the nature of memory and personality, how it is coded, and the events which can destroy it, is likely to take to zero.
We can certainly make discoveries allowing us to definitely state that some memories survive. But will this, at any given time in the future, be for ALL memories and under ALL circumstances? For some time, at least, we would only be able to test for survival of a representative sample, and the criteria by which we decide it is representative will themselves be faulty. Nor are they likely to work for ALL cases of interest: consider again all the repair methods proposed on page 2: any accident involving such methods will need for its repair still more advanced techniques which will not exist at the time. If we come to understand how memory is coded in the brain, then we will adopt technologies to modify that coding, and sometimes by accident or design such technologies will go awry: not merely or simplistically to ERASE memories, but to invalidate the tests we have for the existence of the memory itself.
Nor can we ever expect definitive means to prove that memory is NOT present. Our memories may leave OTHER traces in chemicals or structure of the cell which could allow us, by a kind of archaeology, to reconstruct them. Revival of someone in such circumstances would consist not just of bringing them back to life and health but of endowing their brain cells themselves with new capabilities to recover the memories which would be lost to normal intact brains.
Certainly if we define our circumstances, we can find cases in which memory is virtually certain to be destroyed. Yet in real life, accidents, mistakes, disease do not present themselves in such a well defined way. There is an IRREDUCIBLE UNCERTAINTY which is basic to cryonics, not merely an adventitious consequence of our ignorance about how memory is stored.
If we seriously proposed to take up the freezing of incurably ill or damaged
people, then we will come to freeze people ESPECIALLY if their survival is uncertain,
undefined, or suggested only by indirect criteria.
For someone who wants to know about survival of identity and memory. we can point
out also that such survival is not at all the same as "life" presently so called.
Above, I have given an account of evidence for survival in cases of "death"; but
we have only uncertain evidence for survival in many cases of "life", even now.
Conditions, such as late congenital familial amaurotic idiocy, meningitis, Parkinson‘s
Disease, Jacob-Creutzfeldt disease, all turn normal thinking people into idiots.
Alzheimer's Disease will do the same. What is the evidence for survival
of THEIR memory and identity? Like that of memory after "death", it is necessarily
All of the above was devoted to the evidence for survival, often in very bad circumstances. I said that in normal circumstances, we try hard not to let things go that far.
I will now discuss what can happen in good circumstances. The situation, of course. is not nearly so gloomy.
In the first place, equipment for freezing can be set up and ready while the donor is in failing health. Even if hospital cooperation cannot be obtained, the cryonics societies have their own cardiopulmonary resuscitators, so that no serious danger exists that the brain will be for long without oxygen until it has been cooled.
To understand how you would be frozen in good circumstances, you must understand about the "Declaration of Legal Death". This occurs only by customary practice of physicians, and they have resisted any attempt to define the circumstances legally. Usually it is not discussed openly, even in the medical press.
In general, what happens is that the doctor determines that you are unable to continue breathing and heartbeat on your own. When examined very closely, of course, this criterion becomes very indefinite indeed. lt is certainly NOT the same as "brain death" UNLESS THE PHYSICIAN DELIBERATELY REFRAINS FROM ATTEMPTS TO ARTIFICIALLY SUPPORT BREATHING AND HEARTBEAT. And in fact, most cases of declaration of legal death involve a decision by the physician TO deliberately refrain from artificial support.
1f the cryonics societies are informed, and if they can set up their equipment in advance, and if they have a cooperative doctor on hand, then there will never be ANY QUESTION of brain death. You will be declared legally dead by the cooperating cryonics physician, transferred to the cryonics society CP resuscitator, and then freezing will commence.
What is the chance that you will be frozen in good conditions? A recent book (Life Before Death, by A. Cartwright, L. Hockey, J. L. Anderson; Routledge and Kegan Paul, London and Boston (1973) [HSci: WT 30 C329L]; presents statistics on the warning time available before death. In 83% of all cases, there was more than 1 week's warning before death. The major cause of sudden deanimations is heart attacks and strokes; accidents play a small role (and in fact, in many accidents the victim actually survives for up to a day or more before succumbing). With preparation, your chances of freezing in good conditions are quite high.
However, take note: "Good conditions" here is always a misnomer. If conditions
were really good, you wouldn't have died, would you?
The ideas of cryonics involve the proposal that people be frozen and stored for periods of hundreds of years. Freezing is not itself a treatment for disease; it merely opens the possibility of future treatment to a patient. A close consideration of the kinds of diseases from which we now suffer, and from which we will in future suffer, strongly suggests that freezing would yield very little real benefit to the frozen if we are only willing to contemplate freezing for short times of 20 years or so. Indeed, if we start to freeze people with the intent of doing so only for 28 years. we will be led to storing them for hundreds of years. IF WE PROPOSE TO FREEZE PEOPLE AT ALL, THEN WE WILL CONTEMPLATE FREEZING THEM FOR HUNDREDS OF YEARS. All of the outrageous proposals of cryonics stem from this basic premise.
This basic premise, however, involves also a BASIC UNCERTAINTY which NO AMOUNT of purely technological discoveries will remove at this time. We are now attempting to found SOCIAL INSTITUTIONS which will last for hundreds of years and provide for the revival of people entrusted to their care NOW. Even if someone is successfully frozen and revived in 30 years time, YOUR situation will not be much changed [Editor's note 4]. For it will still not be known that the cryonics societies can survive for the length of time required.
If, again, we propose to freeze and store people so that they can take advantage of future medical progress, WE WILL NEVER BE ABLE TO PROVE TO THEN BEFOREHAND THAT THEY WILL BE CURED AND REVIVED. I do not believe that the prospects of someone facing freezing will be any more predictable on scientific grounds than they are right now, in 1998. It will always be a case of: if we knew how to revive this man then WE WOULD NOT HAVE FROZEN HIM IN THE FIRST PLACE.
To both of these questions, the survival of cryonics societies is essential.
Since cryonics has never happened before, we cannot prove that cryonics societies
are going to survive by any past history. However, many institutions have lasted
a very long time. I collect here some notices of them.
|Westminster Abbey||Founded 1065. Continuously maintained and occupied
since. Earliest tomb, Edward the Confessor (d. 1065), still extant. Many
others: Chaucer (d. 1350); many Medieval nobles and bishops still extant.
Longevity 913 years or more.
|St. Denis, Paris||Line of French kings from Merovingian times until
1792, when during the French Revolution all royal tombs were opened and
the bodies destroyed with quicklime.
Longevity about 1288 years.
|New Kingdom Egyptian tombs||Mummies kept in tombs cut in rock cliffs. Egyptian
Earliest 1578 BC. Tombs continuously maintained by tombs priests until
the Saite dynasty, about 500 BC.
Longevity about 1000 years.
Europe particularly is crammed with tombs in town cathedrals and monasteries. Many more can be listed than I have given here. For instance, the bodies of all English kings since 1215 are still extant (longevity more than 763 years).
Survival of tombs requires a commentary. I DO NOT COUNT periods in which the
tomb was merely existent, but only those in which it was maintained, rites were
carried on, bodies protected, etc. That is why I do not credit the Egyptians
with more than 1000 years of longevity. These figures are for survival BOTH
of bodies AND of an organization to care for them.
|Founded 538 AD, one of earliest Christian monasteries.
Continuously inhabited since that times in Muslim Egypt.
Longevity 1448 yrs or more.
|Monasteries of Mt. Athos
|Inhabited by anchorites from 830. Great Lavra
of Mt Athos founded in 963 AD. Continuously inhabited, including through
the period of Turkish rule.
Longevity 1015 yrs.
|Founded 529 AD. As a corporate body has persisted
in the same location since that time. Sacked by Arab raiders about 800
AD, monks escaped; monastery rebuilt the following year. Bombed during
W.W. II, rebuilt following the war.
Longevity 1449 yrs or more.
|Founded in 361 AD by (St) Martin of Tours, first
monastery in Gaul. Persisted until 1792.
Longevity 1615 yrs.
You will have to decide whether it is the fact that these were religious institutions
which led to their longevity, or whether it is simply that only religious institutions
have existed in the world long enough to have even the possibility of possessing
such longevity. For instance, JOINT STOCK COMPANIES in their modern form began
only about 1880. it is therefore unreasonable to expect such companies to show
a longevity longer than about 178 years. You will also have to decide whether
cryonics will produce loyalty to match that of religion.
As mentioned, corporations in their present form do not have a long history. I list here some which began earlier in some form.
Survival of corporations is hard to evaluates since they may merge with others
while continuing to carry on the same business. lt is not necessary for you
to be revived by the same cryonics societies which saw to your freezing.
In evaluating the possibilities of being stored for a very long time, I have not brought up some important probabilities and interactions.
I wrote this bibliography and commentary in 1976 and used it in Australia from that time on. I am up loading it because I think it still has much more than historical value.
In 1978 the American cryonics societies started distributing it. I changed references to dates, and added some citations, for that edition, which is the one presented here. As for history, many cryonics writings by Saul Kent, Mike Darwin, and others still exist only on hardcopy in rare editions. All of this material, done before the age of the PC, deserves transference to computer media. This bibliography is a fragment from the Dark Ages.
In those days, when cryonics was so difficult, everyone expected freezing in bad conditions. That is why the bibliography spends so much time on freezing in bad conditions. But that is still a problem today: not everyone will be frozen in good conditions, not EVER.
We also understand memory a great deal better now than we did then.
Today, when cryonics is moving out of a period of pessimism, the discussion HOW LONG CAN WE EXPECT TO STAY FROZEN seems unnecessary. Many cryonicists believe revival will come in decades, not centuries. I do not feel that this is necessarily WRONG, but I KNOW that things do not always go well. I feel it is still valuable to know that cryonics can survive for centuries if it has to do so.