Why didn't Dr. Nemur want to use Charlie?

Nemur didn't want to use Charlie in the experiment because he was afraid the increase in IQ would make him sick. He felt Charlie's IQ was too low, and noted that Charlie would be the first subject to undergo the operation.

Prof Nemur was worryd about my eye-Q getting too high from mine that was too low and I woud get sick from it.

Then prof Nemur said remembir he will be the first human beeing ever to have his intelijence increesd by sergery.