One blood donation can save three people. Last year alone in Ukraine, donors gave blood at least 14,000 times. So, over the years — even centuries — of blood transfusion history, millions of lives were saved. This was made possible thanks to animals, namely the first dog-to-dog blood transfusions. Let’s dive into history and learn about the risky and often inhumane experiments that paved the way for modern blood donation — lifesaving and safe.

Liver or Heart: How the Circulatory System Works

Imagine this: it’s the early 17th century. Copernicus has already shown that the Earth revolves around the Sun. Yet people still do not fully understand the workings of their own bodies, particularly the circulatory system. Since Ancient Roman times, the theory of Claudius Galen prevailed, claiming that the liver produces blood and distributes it throughout the body like a centrifuge.

But one man in the Kingdom of England set out to prove that these ideas were incorrect. This was physiologist and anatomist William Harvey. Observing the hearts of living animals, he realized that during systole (the contraction of the ventricles and atria), blood is pushed out. The scientist then demonstrated that valves in the veins allow blood to flow in only one direction — this is how the blood returns to the heart.

Ultimately, William Harvey hypothesized that blood circulates in animal bodies. In the eighth chapter of his book “De Motu Cordis” (“On the Motion of the Heart”), he explained it like this: “…through dissection of the living in order to experiment and through the opening of arteries, from the symmetry and magnitude of the ventricles of the heart and of the vessels entering and leaving… I had very often and seriously though about… how great the amount of transmitted blood would be [and] in how short a time that transmission would be effected… I began privately to think that it might rather have a certain movement, as it were, in a circle….”

Thanks to William Harvey’s research, he discovered and described in his research that:

  • The heart contracts 1,000 times in half an hour, initiating blood circulation;
  • With each contraction, approximately 6 grams of blood pass through the heart, with its total capacity being 43 grams;
  • Blood moves in circles through the system of blood vessels in one direction (from the heart via arteries, and back via veins).

From the Theory of Circulation to the Practice of Transfusion

Following William Harvey’s discovery, the development of this branch of medical science accelerated, and by 1665, physician Richard Lower conducted the first blood transfusion between dogs. For this, he drew blood from a medium-sized dog “its strength was nearly gone” and then transfused blood from two large mastiffs.

The procedure was successful — an outcome tempting enough to try on humans. But there was a catch: at first, doctors experimented not with human-to-human transfusions but with… animal blood. Such attempts were bound to result in losses: animal blood cannot mimic human blood due to differences in the properties of red blood cells across species.

However, some studies found that, among tested animals, sheep blood most closely matches the viscosity of human blood. This explains the documented case of interspecies transfusion without fatal consequences: in 1667, French physician Jean-Baptiste Denys transfused blood from a lamb to a 15-year-old boy and a woman who had recently given birth. Both survived but suffered severe anemia. Not all experimental patients were so fortunate, and some cases resulted in death. Therefore, blood transfusions from animals to humans were soon prohibited.

From Practice to Understanding the Principles of Donation

In 1818, scientist and physician James Blundell performed the first successful and documented human-to-human blood transfusion.

Blundell’s patient was dying of postpartum hemorrhage, so to save the woman, the doctor used her husband as the donor. Between 1825 and 1830, James Blundell conducted 10 blood transfusions, but only half were successful. Why was the blood sometimes unsuitable?

It took science nearly nearly a century to figure out the concept of blood types and how critical they are for successful transfusion. We owe the most to Karl Landsteiner, who in the 1900s described all blood types and received a Nobel Prize for his discovery.

Notably, zoologists contributed to this progress as well. In 1875, one of them, Hermann Landois, discovered that when animal blood is transfused into humans, foreign blood cells “clump together” and break down in the blood vessels, releasing hemoglobin. Between 1901 and 1903, Karl Landsteiner noted that a similar reaction occurs during human-to-human blood transfusions. This can cause shock, jaundice, and hemoglobinuria (abnormal breakdown of red blood cells), as seen during early attempts at transfusion.

At first, this reaction was overlooked. However, in 1909, Karl Landsteiner classified human blood into the now-familiar types A (II), B (III), AB (IV), and O (I). He demonstrated that when blood type A is transfused to a recipient with the same type, blood cells remain intact. But if blood from another type — B or AB — is transfused, the red blood cells are destroyed. Additionally, there are universal donors: people with the blood type O (I).

This is just a brief outline of the journey toward a functional system of blood donation between humans. But let’s admit, we owe many of these great discoveries to animals. So why shouldn’t animals also benefit from science to live longer, healthier lives? Let’s explore blood donation among animals.

Blood Donation in the Animal World

Around the same time when human blood types were being studied, scientists were also researching dog blood types. However, a complete classification wasn’t achieved until the 1950s. For dogs, the DEA system (Dog Erythrocyte Antigen) is used, while for cats, the AB system is applied — somewhat resembling the human blood type system.

Animals that regularly participate in blood donation become true heroes. For instance, a dog named Woodie from Leicestershire, England, saved 88 dogs by regularly donating his rare blood type.

Entire blood banks are already being created to save animals. For example, the Pet Blood Bank operates in the United Kingdom. In Ukraine, similar banks exist based at research institutions, veterinary clinics, or municipal enterprises like Lev in Lviv.

However, due to a shortage of animal donors, scientists are also searching for alternatives to blood products. Currently, synthetic colloids and oxyhemoglobin are being considered, but they are not yet effective. For example, synthetic colloids cannot carry oxygen, and oxyhemoglobin has limitations such as high cost and limited availability. Additionally, this type of hemoglobin performs its function for only 3 days.

Therefore, while researchers continue their work, finding donors must be simplified. For this purpose, UAnimals created the Animal Donor Platform. Those whose cats and dogs can donate blood can register there, as well as those looking for donors for their pets. From there, the process works like a dating app, except the “date” happens in a clinic and is often life-saving for the animal.

The journey to inventing and perfecting blood donation was arduous, filled with mistakes and sacrifices. Let the knowledge gained save as many lives as possible — both human and animal.

Content