Journal ofMedical Ethics 1998;24:18-24

Xenografting: ethical issuesJonathan Hughes University ofManchester, Manchester

AbstractThis paper considers the ethical issues raised byxenotransplantation underfour headings: interferingwith nature; effects on the recipient; effects on otherhumans; and effects on donor animals. The first twoissues raise no insuperable problems: charges ofunnaturalness are misguided, and the risks thatxenotransplantation carries for the recipient are amatterfor properly informed consent. The other twoissues raise more serious problems, however, and it isargued that ifwe take seriously the risk oftransferring new infectious agents from animal tohuman populations and the interests ofdonoranimals, then a moratorium on xenotransplantationis calledfor. The paperfinds that the recent NuffieldCouncil and Department ofHealth reports onxenotransplantation are insufficiently cautious in theconclusions that they draw from these considerations.(7ournal ofMedical Ethics 1998;24:18-24)

Keywords: Xenograft; xenotransplantation; animal welfare

The idea ofusing animals as a source of organs fortransplant into humans has been around for sometime, but until now these procedures have beenbedevilled by problems of immune system rejec-tion: few patients have survived more than a fewweeks and many have died in a matter of hours orless. Recently, however, there has been an upsurgeof interest, resulting from technological develop-ments that offer improved prospects for xenograftrecipients. Better immunosuppressive drugs mayhelp to reduce the rate of rejection, particularlywith organs from closely related species such asbaboons, and genetic modification of donoranimals (particularly pigs) may improve theirorgans' compatibility with human recipients andhence reduce human immune system responses.The ethical arguments in favour of continuing

this research and developing treatments are clearand need little explanation. Although it is possiblethat xenotransplantation will become the medi-cally preferred treatment for some conditions,' themain consideration prompting current interest isthe shortage of donated human organs.Xenotransplantation, it is hoped, will close the gapbetween the number of patients in need of trans-

planted organs and the number of organsavailable. The moral importance of treating morepatients and of finding better treatments shouldbe uncontroversial, so I will not analyse thesemotivations any further. I am not assuming, how-ever, that these are the only considerationsmotivating the development of xenotransplanta-tion, for it is clear that the financial incentives forcompanies to become involved in the develop-ment and supply of xenotransplantation technol-ogy are huge.2 What I am assuming is simply thatthe considerations I have cited provide sufficientreasons for developing xenotransplantation in theabsence of countervailing considerations. Thequestion to be answered, therefore, is whetherxenotransplantation is an acceptable means ofachieving those ends.The ethical problems raised by xenotransplan-

tation will, in this paper, be considered under thefollowing headings: (i) interfering with nature, (ii)effects on the recipient, (iii) effects on otherhumans, and (iv) effects on donors. Other classifi-cations could be used, but this one has been cho-sen in order to highlight the differing ethical statusof considerations falling under each of thesecategories. In exploring these issues it will beargued that although the recent reports for theNuffield Council on Bioethics' and the Depart-ment of Health4 have made important contribu-tions to this debate, both reach conclusions thatare insufficiently cautious in the light of the prob-lems that they address.

1. Interfering with natureThe idea that transferring organs from animals tohumans is unnatural probably explains a greatdeal of the disquiet that many people feel aboutsuch procedures. Explanations, however, are notalways vindications, and in this case objections to"interfering with nature" or "playing God" (to usea related and oft-heard expression) are misplaced.Aside from xenotransplantation, charges of

unnaturalness are often heard in arguments aboutsexual morality and the related medical field ofassisted conception and reproduction. The claimis that certain acts or treatments are unnatural,and therefore wrong. However, it is notoriously

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difficult to define what is natural and what isunnatural. On one account everything thathumans do is by definition unnatural, because itconstitutes an interference with the non-humannatural order. On this account we cannot avoidinterfering with nature, so the suggestion that onecourse of action is unnatural cannot be a reasonfor doing something else instead. On anotheraccount nothing that humans do is unnatural,since humans are themselves a part of nature. Ifnothing we do is unnatural then nothing we docan be unnatural and therefore wrong. It might bethought that these are extreme views on whatconstitutes the natural, and that what is required isthe drawing of an intermediate line, dividinghuman actions into the natural and unnatural.The problem, however, is that it is very difficult tofind a clear and well-motivated place in which todraw such a line, and even if such a line weredrawn, it is not at all clear that the kinds of medi-cal treatment condemned as unnatural, such asartificial conception and xenografting, would fallon one side, with more widely accepted treat-ments such as the use of antibiotics on the other.Indeed, the fact that a proposed boundary woulddivide medical treatments in this way might wellbe taken as a reason for regarding the line as anarbitrary one.

"Natural" factsA second problem with the condemnation of"unnatural" procedures is that even if we can dis-tinguish what is natural from what is not, it isunclear why we should prefer the former andregard interference with nature as wrong. JohnStuart Mill famously opposed this view by point-ing out that nature's powers "are often towardsman in the position of enemies, from which hemust wrest by force and ingenuity, what little hecan for his own use".5 It is only by interfering withnature that we can free human lives from thedestructive effects of such natural phenomena asinfectious agents, droughts and hurricanes.

Nevertheless, the distinction between the natu-ral and the unnatural seems important to manypeople, and an explanation of this has recentlybeen proposed by Richard Norman.6 His sugges-tion is that we need a background of "natural"facts-facts that we think of as beyond ourcontrol-in order to give meaning and value toour choices. It is because of the enduring reality ofhuman sickness and pain, aging and death, thatattempts to prevent or mitigate these evils in par-ticular cases have meaning. We may aim for aworld without pain, but if we achieved it certainvaluable kinds of action would cease to bepossible, and if there were no facts of life beyond

our control then our lives would lack the structurethat makes the idea of choice intelligible. Environ-mental ethicists have similarly argued that wilder-ness areas, created by natural processes andunchanged by human agency, are to be valued forproviding us with a "larger context", something"outside of ourselves", in which to situate theplans and projects that comprise our lives.7 How-ever, while the need for a background againstwhich to locate our choices and actions mayexplain our attachment to an idea of the natural, itdoes not provide us with a reason to reject proce-dures such as IVF or xenografting.

Human biologyThe charge of unnaturalness in relation to IVFand related procedures is prompted by the fearthat such developments (like the use of contracep-tion according to Roman Catholic teaching) willdestroy the connection between sex and procrea-tion which gives sex its particular significance, butas Norman points out, these developments arevery far from destroying that connection at a gen-eral level. Similarly it might be suggested thatxenografting will destroy the way in which humanlives are structured by their dependence upon theparticular characteristics and limitations ofhuman bodies. Once again, however, the fear isoverstated: our lives are structured by the natureof our bodies, but a part of that structure consistsof the incentive that we have to struggle againstparticular limitations. Xenografting, along withother medical procedures, is one of the means bywhich we may pursue that struggle, and even if itwere to become a successful and widespread formof treatment we would be a long way from puttingthe struggle behind us and severing our depend-ence upon human biology.Another worry about naturalness, raised by the

Nuffield Report, concerns the way in which apatient's self-image might be affected byxenotransplantation:"One cause ofunease is the breaching of normallyinviolate boundaries. This is seen in human organtransplantation. The recipient of a transplantedorgan may feel that the boundary between self andnon-self has been breached. ... With xenotrans-plantation, an additional boundary, that betweenhuman and animal, may become blurred."8The force of this point is that the worriesdescribed may be a real source of harm to recipi-ents of animal organs, irrespective of whether theworries are well-grounded. In the light of my pre-vious comments we may judge it irrational toregard receipt of a xenograft as a dilution of one'shumanity, or to regard it as being qualitatively

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20 Xenografting

different from the use ofhuman organs, prosthet-ics or any other medical modification of thehuman body. It may therefore be that discussionof these issues in the course of counselling willcause such worries to disappear. On the otherhand the worries may remain, despite counsellingand despite the lack of a rational grounding, caus-ing serious detriment to a patient's wellbeing. Ifthis proves to be the case, then it is a real objectionto xenotransplantation, at least in patients thoughtprone to such worries. However, this is not funda-mentally an objection based on the unnaturalnessof xenotransplantation (since the objection isindependent of the truth of that charge), but onewhich properly belongs with the next set of prob-lems to be considered, problems arising from thedetrimental side effects (in this case the psycho-logical side effects) that xenotransplantation mayhave upon the recipient.

2. Effects on the recipientIn any medical decision, the benefits that thepatient stands to gain from a treatment must bebalanced against its risks. Given the experience ofxenotransplantation to date, the risks to recipientsof animal organs must be considered verysubstantial. One kind of risk-the risk of psycho-logical damage associated with a changed self-image-has already been mentioned, but the mainrisks to xenograft recipients are the risk ofrejection, the increased risk of infection resultingfrom immunosuppression, and the risk of diseasestransmitted from the donor animal. None of theserisks is unique to xenotransplantation, all beingproblems for human organ transplants as well,though the first two risks are likely to be greater inthe case of xenotransplantation: the risk ofrejection is higher, and consequently higher levelsof immunosuppression are likely to be needed.The risk of disease transmission is hard toquantify, a point which I will return to in the nextsection.The main ethical issue raised by these risks is

that of consent. It is vital that potential patients aremade aware of the risks before agreeing to thetreatment, but so long as only the patient's inter-ests are at stake, and the patient is fully aware ofthe potential benefits and risks of treatment, thepatient's autonomous decision ought to deter-mine his or her treatment. This assumes that thepatient is capable of making an autonomouschoice, and for this reason both the Nuffield andDepartment of Health reports recommend thatearly xenografts should be given only to compe-tent adults.9 It is also necessary to ensure that thepatient's decision is freely made, and to safeguardthis the reports recommend that patients who

refuse xenografts should remain eligible forhuman organs on the same basis as before.'0

I have suggested that as long as the choice oftreatment affects only the interests of the patient,the patient's choice should be respected. Thisview, however, is not universally shared. It is heldby some that there are limits to what peopleshould be allowed to consent to. It might beargued, for example, that the prospects forxenograft recipients are at present so poor that itwould be wrong to carry out further procedureseven with the recipients' full consent. The mostplausible basis for this view is that there are somerisks that it cannot be rational to accept-and thatthe fact that a patient does consent to them is evi-dence that he is desperately clutching at strawsand incapable of making a rational choice. Butwho is to say that it is irrational for a patient in adesperate situation to accept desperate odds?Acceptance ofhigh risks may indicate an impairedcapacity to make rational choices, but judgmentsof a patient's competence must be made on morethan this evidence alone.Another putative reason for limiting what

people are allowed to consent to arises when weconsider the experimental nature of currentxenotransplantation procedures. At present theprognosis for xenograft recipients is very poor, butit is hoped that this will improve as experience isgained, as has happened with human organ trans-plants. The danger here is that patients will beencouraged to accept greater risks than wouldusually be judged in their interests, for the benefitof future patients. This possibility clearly rein-forces the need to ensure that patients are properlyinformed before agreeing to participate, and thattheir consent is freely given, but there is also awidely held view that patients should not bepermitted to consent to participation in medicaltrials unless it is judged that there is a reasonableprospect of their benefiting from the treatment.This is a controversial view since, on the face of it,it appears to prohibit heroic altruism"; however, Imerely wish to note here that what makes experi-mental treatments controversial is the fact that it isthat it is not only one person's interest at stake: therisks and benefits may accrue to different people,allowing the prospect of one person's interestsbeing sacrificed for the benefit of another.

3. Effects on other humansThe separation of risks and benefits becomesclearer when we consider the next set of ethicalproblems raised by xenotransplantation: theeffects on humans other than the recipient. Themost important issues here are the risk thatdiseases transmitted from animals to humans may

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prove infectious between humans, leading perhapsto new AIDS-type epidemics, and the costs thatwill be borne by other patients if resources are

redirected from other areas of medical researchand treatment to fund xenotransplantation. Thefact that xenotransplantation carries risks not justfor the xenograft recipient but for the populationgenerally is important because it takes the ethicsof xenotransplantation outside the realm ofindividual consent and into the realm of justice,raising questions about the extent to which it ispermissible for an individual to impose risks on

others for his own benefit.The issue of reallocating resources is not

specific to xenotransplantation, but raises thesame problems as the introduction of any othernew and experimental treatment-problems ofpredicting future costs and benefits and of ensur-

ing effective and equitable use of resources. Thequestion here is whether xenotransplantationwould be a better or worse use of resources thanthe available alternatives.

More serious problemThe risk of transmitting infectious diseases to thewider population, however, is an altogether more

serious problem. We do accept the imposition ofsome risks on others for our own benefit (forexample when we drive cars). However, there are

limits to what we regard as acceptable (it is notacceptable, for example, to drive when drunk),and it is therefore necessary to consider the natureof the risk imposed on the wider population byxenotransplantation procedures. The difficulty forproponents of xenotransplantation is that theworst-case scenario (a major new epidemic) isextremely grave, and its likelihood is difficult ifnotimpossible to quantify. As the Nuffield reportexplains:

"It will be very difficult to identify organisms thatdo not cause any symptoms in the animal fromwhich they come. Previous experience indicatesthat infectious organisms are normally identifiedonly after the emergence of the disease they cause.

... Put bluntly, it may be possible to identify anyinfectious organism transmitted by xenograftingonly if it causes disease in human beings, and afterit has started to do so."''2

Moreover, if, as in the case of HIV, there is a longincubation period between infection and develop-ment of the disease, the agent may have spread farbeyond the original xenograft recipient by thetime its symptoms are noticed, undermining anyhope of containing the infection. The Nuffieldreport concludes from these considerations thatthe risk of a major epidemic is unquantifiable,'3

and in the light of this advocates a precautionaryprinciple, requiring "that action should be taken toavoid risks in advance of certainty about theirnature" and that "the burden of proof should liewith those developing the technology to demon-strate that it will not cause serious harm".'4Unfortunately, the measures that the reportproposes in order to safeguard against diseasetransmission do not live up to this principle.The report begins robustly enough, by stating:

"that the risks associated with possible transmis-sion of infectious diseases as a consequence ofxenotransplantation have not been adequatelydealt with. It would not be ethical, therefore tobegin clinical trials of xenotransplantation involv-ing human beings"."However, the report goes on to suggest thatxenotransplantation should be allowed to proceedonce the following conditions have been satisfied:(1) that "as much information as possible" beassembled about the risks of transmission; (2) thatsource animals be "reared in conditions in whichall known infectious organisms are monitored andcontrolled"; (3) that early recipients undergoregular monitoring and testing; and (4) that therebe "a commitment to suspend, modify or, if nec-essary, discontinue xenotransplantation proce-dures at any signs that new infectious diseases areemerging". These precautions, however, are farfrom watertight, for, as noted above, the reportacknowledges that full knowledge of potentiallyineffective agents is for all practical purposesimpossible. A consequence of this is that sourceanimals cannot be freed from all infectious organ-isms but only those that are known and can bereliably tested for: "Specified pathogen-free ani-mals may still be infected with unidentified infec-tious organisms about which nothing is known".'6Because the risk of disease transmission cannot beeliminated, the report recommends that proce-dures for monitoring of recipients be establishedand that consent to this be included in consent tothe xenograft. Monitoring, however, is of no useunless backed-up by a plan of action, and as thefollowing passage demonstrates, the report failsutterly to provide such a plan."The most difficult question is what procedureshould be followed if it is found that a disease hasindeed been transmitted from the animals used toprovide organs or tissue to human xenograftrecipients? In principle, steps should be taken toprevent transmission of the disease to otherpeople. In practice, this is a very difficult issue. Fora start, it is very unlikely that, at the outset, themode of transmission of the disease will be

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22 Xenografting

understood. The appropriate response will de-pend on the mode of transmission and on howinfectious the disease is. It would hardly beacceptable to isolate xenograft recipients sufferingfrom an infectious disease, or to ask them torefrain from sexual intercourse or, in the case of avirus transmitted from parent to offspring, fromhaving children. This highlights how difficult itwould be to prevent the transmission of an infec-tious disease originating from xenotransplanta-tion. It is sobering to reflect on the difficulty,despite globally coordinated attempts, of control-ling and eliminating infectious diseases such asmalaria, hepatitis and AIDS".'7This is indeed a sobering passage, and given suchpessimism about the prospects for containment ofany new infection, the precautionary principlewould appear to require that the proposed mora-torium on xenotransplantation procedures bemade indefinite.The Department of Health report goes further

than the Nuffield report in discriminating the risksposed by different kinds of infectious agent, butreaches similar conclusions. Fungi, parasites andbacteria, it concludes, pose relatively little riskeither to the xenograft recipient or to the widerpopulation.'8 With regard to prions, it holds thattransmission to xenograft recipients is unlikely(though recent controversy about the transmissi-bility of prion disease from BSE-infected cattle tohumans might lead us to doubt the reliability ofscientific advice on this matter), and that prionsare unlikely to be transmitted from one human toanother. In view of the latter, the long incubationperiod typical of prion disease appears as anadvantage rather than a disadvantage, allowingthat even an infected recipient may benefit fromyears of good quality life, without posing a risk toothers."' The greatest risk, the report concludes, isfrom viruses, due to their transmissibility betweenhumans, the long incubation periods ofsome viralinfections, and our limited ability to screen for andexclude known and unknown viruses in donoranimals. As far as viruses are concerned, theDepartment of Health report concurs with theNuffield report that the risk of infection andonward transmission is at present too great to jus-tify experimental procedures.

Future acceptabilityUnfortunately the Department of Health reportruns into the same difficulties as the Nuffieldreport in considering the future conditions underwhich xenografting might become acceptable. Ittoo premises the future acceptability ofxenotrans-plantation upon the hope that further research

may show the risk of infection to be "within toler-able margins", while acknowledging that it cannotever be totally ruled out.20 In expressing this hope,however, the report ignores the difficulty, raised bythe Nuffield report, of quantifying, and assessingas tolerable, a risk posed by agents that are as yetunidentified. The Department of Health reportalso follows the Nuffield report in advocatingmonitoring of xenograft recipients as a furthersafeguard against the spreading of infections and,again, like the Nuffield report, offers no satisfac-tory account of what should be done in the eventof a positive result, suggesting only that "appropri-ate additional research" may be indicated.2'

4. Effects on donor animalsSo far I have considered the ethics of xenotrans-plantation in terms of its significance for humans,but of course much of the controversy surround-ing this issue arises from concerns about theimposition ofharms upon non-humans for humanbenefit. Like the non-recipient humans at riskfrom transmitted diseases, the donor animals arenon-consenting parties who stand to be harmedby a procedure designed to benefit others. In thecase of animals, however, a greater degree ofimposed sacrifice is widely held to be acceptable.The problem for advocates ofxenotransplantationis to justify this intuition and to quantify thedegree of sacrifice that may permissibly beimposed.One way of addressing the latter would be to

look at other ways of treating animals about whichwe have clear views, and to ask whether the use ofanimals in xenotransplantation is more or lessacceptable than these. For example, we mightconclude that if it is acceptable to raise and killanimals for food, then it must be acceptable toraise and kill them for medical purposes, sinceeating meat is a luxury whereas xenotransplanta-tion and medical research are often matters of lifeand death. A weakness in this argument is that weare not all agreed on the acceptability of eatingmeat, so the method is unlikely to generate anagreed conclusion. Moreover, even if we assumeagreement on the acceptability of meat consump-tion, the comparison between this and xenotrans-plantation may not be as straightforward as itseems, since xenotransplantation is likely to intro-duce particular animal welfare problems that arenot present (or not necessarily present) in theraising of animals for food. For example, the needto keep donor animals free (as far as possible)from infectious agents may require them to beraised in isolation, and the genetic modificationnecessary to achieve compatibility with humansmay impair health and cause suffering in the

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donor animals. And, in addition to the donor ani-mals themselves, significant numbers of animalswill be needed as experimental subjects in order todevelop the necessary genetic manipulation andtransplantation techniques, and to investigate thedangers of disease transmission. It follows, then,that since the animal harms as well as the humanbenefits of xenotransplantation may be greaterthan those of meat-eating, a simple inference fromthe permissibility of the latter to the permissibilityof the former will be invalid. A different approachis therefore needed in order to justify the sacrificeof animal interests required by xenotransplanta-tion procedures.

Mental capacitiesJustifications for both medical and culinary uses ofanimals typically appeal to the different mentalcapacities ofhumans and other animals. Imposingharms on animals in order to benefit humans isacceptable, it is argued, because the harms andbenefits that humans are capable of experiencingare greater than those that can be experienced byother animals. The physical pains suffered by ani-mals, according to this argument, are lesssignificant than those suffered by humans, be-cause animals are less sensitive, or because theylack the capacity for fearful anticipation ordistressing memory which amplify the effects ofphysical pain in humans. And death matters lessfor animals, it is argued, because animals have lessto lose than humans in the form of potential forfuture pleasures and satisfactions, or because theloss of these things matters less to creatures wholack our capacity to foresee, desire and plan forthem. Both the Nuffield and Department ofHealth reports appeal to arguments of this kind inorder to justify xenotransplantation, citing the dif-ferent capacities of different species in support ofthe view that it is acceptable to use pigs, but notprimates, as xenograft donors:

"When considering the use of primates forxenotransplantation, the capacities they sharewith human beings, notably their self-awareness,led to ethical concerns about their use forxenotransplantation. While unquestionably intel-ligent and sociable animals, there is less evidencethat pigs share capacities with human beings tothe extent that primates do. As such, the adverseeffects suffered by the pigs used to supply organsfor xenotransplantation would not outweigh thepotential benefits to human beings".22Unfortunately for the reports, this kind ofargument is vulnerable to a well-known objection.The problem is that capacities for pleasure andpain, fulfilment and suffering vary not only

between but within species, including humans. Sowhile it is true that the capacities of a normal adulthuman exceed of those of a pig, the same cannotbe said for all humans. There are many whosemental capacities are severely and tragicallyimpaired, and it follows that if we are prepared totake organs from animals on the grounds of theirlimited capacities we should also be prepared totake the organs of those humans whose capacitiesare similarly restricted. Or conversely, if we insistthat we should not take organs from such humans,then consistency demands that we refrain alsofrom taking the organs of animals with similar orgreater capacities.

This point about the overlapping capacities ofhumans and other animals is most often advancedas an argument against the use of animals, in, forexample, medical research.2' An exception, how-ever, is its use by RG Frey, who suggests thatexperimentation on animals is too valuable to dowithout, and that we should therefore bite thebullet and accept the use of some severelymentally impaired humans as experimentalsubjects.24 Applied to xenotransplantation, Frey'ssuggestion is that we should accept the killing ofsome mentally impaired humans for their organsrather than forgo the benefits of xenotransplanta-tion. Now this, for many, will be too much toaccept, and it will be held that we must do withoutvivisection or xenotransplantation if the only con-sistent alternative is to accept that mentallyimpaired humans as well as animals may be usedfor these purposes. Others will argue that even ifwe were to accept Frey's stance in principle, thedifficulties of measuring and comparing mentalcapacities across species would make it impossibleto judge which humans should be used in prefer-ence to which animals. It may be, however, thatamong the possible ways of reforming our proce-dures for procuring human organs there are somewhich do not involve unacceptable human costs,and which can reasonably be judged to be morallypreferable to xenotransplantation.

Opting-out systemI have in mind reforms which would increase thesupply of organs from humans who lack anycapacity for suffering, either because they are deador because they have lost, or never had, any higherbrain function. These reforms could include,firstly, a relaxation of the requirement for consentin obtaining organs from cadavers, by removingthe relatives' veto and moving to an opting-outsystem, with opt-outs perhaps restricted to thosewith a conscientious objection. Secondly theycould include relaxation of the whole-brain crite-rion of death, in order to allow removal of organs

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24 Xenografting

from anencephalic infants and patients in persist-ent vegetative states.` Although these proposalswould involve only donors who are lackingconsciousness and therefore incapable of beingcaused suffering, it might be objected that suchmeasures would result in distress for otherhumans: relatives, onlookers and other thirdparties. However, we would have to judge thatanimals' interests matter very little indeed for thedirect harm that xenotransplantation would im-pose on them to be outweighed by the third-partyconcerns of some humans. This is especially truewhen we consider that the use of animals wouldalso be likely to cause distress amongst humanonlookers, as a result of and in addition to thedirect harms imposed on the animals, and thatgiven the absence of any such direct harm in thehuman case, the third party distress factor wouldbe likely to diminish as the new practices becamemore established.The suggestion that measures for increasing the

supply of human organs be explored beforeresorting to xenotransplantation is also supportedby the arguments of the previous section, since itwould avoid - or at least postpone - the risk oftransmitting infectious diseases from animals tothe human population. Whether such measureswould be sufficient to close the organ gap isuncertain, but the conclusion to which we are led,if we take seriously both the interests of animalsand the risks of disease transmission to humans, isthat a moratorium should be imposed uponxenotransplantation procedures at least until pos-sible avenues for increasing the supply of humanorgans have been exhausted and until a morereassuring judgment can be reached on the pros-pects for preventing and containing transmittedinfections.

Jonathan Hughes, BA, PhD, is Lecturer in PoliticalThought, Department of Government, University ofManchester.

References and notes1 Nuffield Council on Bioethics. Animal-to-human transplants: the

ethics of xenotransplantation. London: Nuffield Council onBioethics, 1996:27.

2 Costing xenotransplantation. Bulletin of Medical Ethics 1996;Mar:3.

3 Nuffield Council on Bioethics. Animal-to-human transplants: theethics of xenotransplantation. London: Nuffield Council onBioethics, 1996.

4 Advisory Group on the Ethics of Xenotransplantation. Animaltissue into humans: a report by the Advisory Group on the Ethics ofXenotransplantation. London: Stationery Office, 1997.

5 Mill JS. Three essays on religion. London: Longmans, Green &Co, 1904:15.

6 Norman R. Interfering with nature. Journal ofApplied Philosophy1996;13.1:1-1 1.

7 See for example Goodin RE. Green political theory. Cambridge:Polity Press, 1992.

8 See reference 3:§9.12. See also reference 4:§7.14 for a moregeneral comment on the psychological and social impact ofxenotransplantation on the recipient.

9 See reference 3:§§7.23, 7.25; reference 4:§7.7.10 See reference 3:§§7.30, 7.31; reference 4:§7.15.11 Perhaps for this reason the Department of Health report holds

back from endorsing such a restriction. Its view appears to bethat any trial conducted, considered as a whole, must offer theprospect of therapeutic benefit to patients, while leaving openthe possibility that those trials may include volunteer partici-pants in whose individual cases benefit is unlikely. See reference4:§§7.5, 7.6.

12 See reference 3:§6.14.13 In the words of the Nuffield report: "It is not possible to predict

or quantify this risk but, in the worst case, the consequencescould be far-reaching and difficult to control". Reference3:§6.20.

14 See reference 3:§6.21.15 See reference 3:§6.23.16 See reference 3:§6.30.17 See reference 3:§6.36.18 See reference 4:§4.54.19 See reference 4:§4.55.20 See reference 4:§§4.62, 4.63.21 See reference 4:§§4.68, 4.63.22 See reference 3:§4.42. Similar statements can be found in refer-

ence 4:§§4.28-4.30. Both reports, however, approve the use ofsmall numbers of primates as recipients of organs fromnon-primate animals during research into xenotransplantation.

23 The best-known proponent of this argument as an objection tovivisection and other uses of animals is Peter Singer. See, forexample, Singer P. Practical ethics. Cambridge: Cambridge Uni-versity Press, 1993:65-8.

24 Frey R G. Medicine, animal experimentation, and the moralproblem of unfortunate humans. Social Philosophy and Policy1996; 13.2:181-211.

25 This could take the form either of a redefinition of death, or adropping of the requirement that patients be dead beforeremoval of organs in favour of the requirement that they havepermanently lost consciousness. The latter is recommended inSinger P. Rethinking life and death. Oxford: Oxford UniversityPress, 1995.

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