John Haslam 
Observations on Madness and Melancholy — Including Practical Remarks on Those Diseases; Together With Cases; And an Account of the Morbid Appearances on Dissection [EPUB ebook] 

Observations on Madness and Melancholy by John Haslam is an authoritative work on madness, insanity and melancholy — terms that are used in the pejorative in most circumstances. Haslam provides the definitions, symptoms and observations for these medical conditions. The unique characteristic of this book lies in its ability to provide a clear understanding of madness as a disease and giving it a concrete form by bringing it out of the abstract. (Goodreads)