It is very difficult to write about the history and past events that have happened thousands of years ago, because one should take into account all the factors that are not comprehended by the modern person. Take, for example, the factor of society development. Europe is the continent which has the highest level of literacy among its citizens. Just a few centuries ago the majority of the population in Europe was illiterate, and even the very notion of literacy have passed a long-term development. The current meaning is different from its original meaning, which had been used, for example, since the 8th century BC in ancient Rome. And these factors are many.
That is why, when I write about history I have to explain what this concept means in general in this context. My personal opinion is that still no one knows the real history of hirudotherapy that goes back to the ancient ages in antiquity, medieval history and early modern times, and its description is therefore a partial short list of publicly available information, obtained from preserved and published investigations and resources.