Describe chillingworths method for treating illness

The use of the term "leech" to describe Chillingworth is at once appropriate and ironic. After all, he is a physician, and leeches at the time were used in order to facilitate bloodletting. At the same time, however, Hawthorne is obviously suggesting the parasitic relationship between Chillingworth and Dimmesdale. Many of his "medicines" are from gathering plants which slowely poison Dimmesdale.