Is this a misprint or old form of dietetic?

From Flatland again:

The art of healing also has achieved some of its most glorious triumphs in the compressions, extensions, trepannings, colligations, and other surgical or diaetetic operations by which Irregularity has been partly or wholly cured.

http://www.alcyone.com/max/lit/flatland/7.html

Bingley

Bingley