Cataloguing Diseases (Genera morborum)

According to Linnaeus’ Clavis medicinae (1766), the study of diseases (pathology) comprised etiology, semiology (the study of symptoms), diagnostics, and prognostics. Was there anything distinctive in what Linnaeus contributed to medical research? Linnaeus placed high demands on medical research. He regarded it as part of natural science, and it should methodologically follow the same rules, that is, diagnosis and treatment should be based on experiments and observations. Preconceived notions and matters of faith should be countered by knowledge of the structure and functions of the body. Rational treatment and prevention of diseases are drawn from facts based on anatomy, botany, chemistry, and physiology, as Linnaeus saw it. In his practice as a physician, his goal was to sharpen his ability to observe scientifically. At the same time, he emphasized the importance of tolerance, in that the interpretation of cause and effect required some leeway as long as there was a gap in knowledge and a hope to gain new knowledge.

Each disease should be viewed on the basis of its:

1. signs (signa), that is, symptoms,
2. essence (essentia), which referred to the origin of the symptoms (e.g. inflammation of the lungs),
3. cause (causa), what produces the disease.

To understand the cause of diseases, Linnaeus felt it was necessary to have a system in which various diseases can be grouped. This grouping can be done in regard to symptoms and observations made in autopsies. Linnaeus had experience from botany in cataloguing and setting up systems. He used this experience to create a system for diseases (Genera morborum). Here he listed diseases in orders, classes, and families with regard to certain diagnostic symptoms. When Linnaeus arranged his system, he was influenced by two contemporary scientists that he had close contact with: the French researcher Francois Boissier de Lacroix, (1706–1767; he called himself Sauvages), who had set up a “Nosologia methodica” and the Dutchman Herman Boerhaaven (1668–1738).

It should be pointed out that the grounds of classification, viewed from the perspective of today, were not accurate, but they did stimulate observers to pay attention to details in the pattern of symptoms and also provided an overview of pathology, constituting an attempt to order the principles of treatment. Linnaeus’ system was primarily based on patterns of symptoms. For fevers he followed another basis for classification (mode of transmission, course of disease): fevers with rashes, critical fevers, and fevers stemming from inflammation.