Chapter 5, ‘Sweat it Out’, focusses on the concept of “insensible perspiration” and the sudorific drug of sal ammoniac.
The existing historiography of insensible perspiration has stressed the longevity of the use of Santorio Santori’s famous weighing chair and of the method of quantification in medicine. And indeed, this chapter confirms that the ancient notion of insensible perspiration continued to be perceived as essential to the maintenance of one’s bodily health in the eighteenth century. Looking at the extensive yet little studied Dutch reception of Santorio’s insensible perspiration, this chapter argues that the works of Johannes de Gorter reveal a drastic shift in thought about insensible perspiration.
Despite its emphasis on quantification in medicine, Santorio’s work still reflected long-standing views on perspiration which were closely aligned to digestion and health as balance of humours. In the eighteenth century, however, physicians of the Boerhaave school paid particular attention to the role of microscopic nerves in the body and to the nature of individual and invisible bodily fluids, such as “nervous juice”. De Gorter’s study on perspiration incorporated neurological descriptions into its attempt to develop a more detailed theory of the internal physiology of perspiration. Furthermore, it allowed him to describe the pathology of diseases like catarrh, and to justify the efficacy of his preferred treatment – sal ammoniac – which would make his patients sweat profusely and, literally, sweat out the disease.