Friedrich Nietzsche book On the Genealogy of Morality
The curve of human capacity for pain actually does seem to sink dramatically and almost precipitously beyond the first ten thousand or ten million of the cultural elite; and for myself, I do not doubt that in comparison with one night of pain endured by a single, hysterical blue stocking, the total suffering of all the animals who have been interrogated by the knife in scientific research is as nothing.
Essay 2, Section 7
On the Genealogy of Morality (1887)