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After the trial, Denys quit his practice and never experimented with blood transfusion again. His practice fueled a considerable controversy in the country, and by 1670, France banned any experimentation and medical procedures involving animal blood.
It is said that Denys’ first two patients survived because of the small amount of animal blood given to them and that neither patients had an allergic reaction or infection. The process of inter-species blood transfer is called Xenotransfusion and is not considered to be a safe way to transfuse blood as it poses a high risk of transmitting infectious diseases. On the other hand, Denys’ succeeding patients received more than one round of transfusion. The additional doses of blood administered for the second and third time were the likely cause of his other patient’s death, except Mauroy who died of poisoning.
Despite Denys’ errors in performing the transfusion, his experiments still contributed to the progress and science of blood transfusion. In 1902, Austrian biologist Karl Landsteiner established the four main blood groups and developed a better process of blood transfusion that is safe and effective for both donors and patients.