At that time, donor organs were not available and the use of animal organs seemed promising.

Hopes were raised further in 1972 with the introduction of cyclosporin, a powerful drug that minimises the rejection of foreign tissue. Until 1992, organs generally came from chimpanzees or baboons, but in that year a pig liver was used to help a patient survive whilst a human liver was found.

Chimps: Close relatives of humans

In 1995, the first genetically-altered animal organs were used. The pig livers were designed to be less prone to attack by the human body and were attached to patient's circulation but kept outside their body.

So far no animal to human transplant of a whole organ can be considered successful.

1682: Bone from a dog was used to repair the skull of an injured Russian aristocrat. The operation was reportedly a success but angered the church.

1963-4: Baboon kidneys were grafted into six patients by transplant pioneer Thomas Starzl in Denver, US. The patients survived between 19 and 98 days.

1963-4: Chimpanzee kidneys were transplanted into 12 patients in New Orleans, US. Most failed within two months but one recipient survived for nine months with no sign of rejection.

1964: A 68-year-old man received a chimpanzee heart in Jackson, US, but only survived for two hours.

}1969-1974: Three children received chimpanzee livers but only survived between one and 14 days.

Baboons: Less expensive to rear than chimps

1977: A 25-year-old woman had a baboon heart transplanted in Capetown, South Africa, and a moderate circulation was maintained but only for six hours before acute rejection. The same group also used a chimpanzee heart to assist the heart of a 60-year-old man. But despite high doses of immunosupressant drugs the patient died after four days.

1984: The Baby Fae case: A newborn baby received a baboon heart in California. Cyclosporine was used and she lived for 20 days.

1992: A four-drug cocktail assisted a baboon liver transplant. The patient died of a brain haemorrhage after 71 days. The type of rejection typical in cross-species transplantation was not seen.

1992: A pig liver was implanted next to patient's own liver to buy time for a human organ to be found but the patient died after 32 hours.

1993: Baboon bone marrow and kidney transplant carried out in Pittsburgh, US with same drug cocktail used as in 1992 case. However, the patient's suppressed immune system succumbs to infection after 26 days.