Sentence:  Men of both these types abound in medicine especially, aside from the great mass of the unlearned, who, if perchance they have heard some mechanistic explanation of Descartes's and badly comprehended it (for indeed the whole system of Descartes is far above their heads), or if (bemused by the tricks of certain smoke-peddlers) they have learned to make some trifle at great cost with the aid of an evil-smelling <WSD>torrefaction</WSD>, they declare themselves not merely philosophers but the only wise men and cultivators of true medicine. 
Meaning of the word marked with <WSD> tags:  The act or process of subjecting something to heat or to highly acidic substances.