The Rebellion of Acid: The Death of Black Bile in the Body’s Laboratory and the Lymph Theory

While fear of contagion and plague hysteria dominated the streets of 17th-century Europe (Days 51 and 52), one of the greatest revolutions in medical history was brewing in the quiet laboratories of universities. The “theory of humours”, shaken by the anatomical genius Vesalius’s cadaver studies, was about to receive its final blow with Gaspare Aselli’s discovery of milk-white lymphatic vessels.

The body is not theology, but a chemistry laboratory

Professor François de le Boë Sylvius (1614-1672) was a brilliant scientist who transformed medical education from top to bottom at the renowned Leiden University in the Netherlands. By establishing Europe’s first university chemistry laboratory, he proved that medicine was not merely dusty shelves and philosophy.

The movement led by Sylvius, Iatrochemistry (Medical Chemistry) , described diseases not as “spirits taking offence”, but as “an imbalance of chemical compounds”. This was a very early herald of modern biochemistry and systemic oncology.

The “Acidic Lymph” theory: a chemical rebellion inside the tumour

The lymphatic vessels discovered by Aselli formed a new map of cancer’s origins in Sylvius’s mind. Sylvius argued that lymph was normally a healing, white fluid that nourished the body. When things went wrong, however, this “milk” became a poisonous weapon.

Cancer was no longer described as the work of an imaginary “black bile”, but as a tangible problem involving coagulation and acidification in the lymph channels. This conceptual leap would guide oncology for approximately 200 years, until the emergence of cell theory (19th century).

A new perspective in oncology: neutralising acid

The Lymph Theory also rationalised physicians’ approach to cancer treatment. If the problem was acidic coagulation, the treatment strategy had to be chemical too: use “alkalis (bases) that would neutralise the acid” and clear the obstructed lymphatic highways.

Today, modern oncology tells us that, although the mechanism Sylvius described was incorrect, it is a scientific fact that the tumour microenvironment truly has an acidic pH and that this acidity promotes tumour growth. This “chemical intuition” of the 17th century would resurface centuries later as an immunological finding.

In our next article (Day 54), we will meet Jan Baptist van Helmont, who was the first in history to describe this cellular rebellion as a “local uprising” and argued that enzymes in the stomach and a “maddened inner spirit” triggered cancer.