Too much to count. I was going to post most here, but Jung already opens up his section on introverted Thinking by relating it to introverts in general.I do remember reading something Jung said on the subject, like you mentioned, but I can't recall the details. What was it exactly?
Like every introverted type, he is almost completely lacking in that which distinguishes his counter type, namely, the intensive relatedness to the object. In the case of a human object, the man has a distinct feeling that he matters only in a negative way, i.e., in milder instances he is merely conscious of being superfluous, but with a more extreme type he feels himself warded off as something definitely disturbing. This negative relation to the object-indifference, and even aversion-characterizes every introvert; it also makes a description of the introverted type in general extremely difficult.