A sentence that I don't understand
Solution 1:
With the OP's explanation that this relates to the Harvard Psilocybin Project:
It appears that the graduate students were testing psychedelic drugs on themselves, so their desks had been moved away to make room for mattresses to lie on, and supplies of the drugs arrived regularly from the manufacturers, Ciba.
The two occurrences are mentioned in the same sentence because they are significant things that Mischel remembers about that period.