This section is from the book "The Hygienic System: Fasting And Sun Bathing", by Herbert M. Shelton. Also available from Amazon: The Hygienic System Vol III Fasting and Sun Bathing.
These are interesting studies during a fast. The tongue becomes heavily coated in almost every instance (I have seen five or six exceptions) and remains so throughout the fast, gradually clearing up, beginning at the edges and the point, until, when hunger returns, it is clean.
The breath becomes very foul and remains so during most of the fast, gradually becoming less so as the work of purification proceeds, until, with the return of hunger, it is sweet and clean. The more foul is a man's body, the more foul will be his breath and the more heavily coated his tongue.