As hard as it is to prove a negative, this individual and their quote appear to have been invented for the story.
The Quote
There's no other reference to that quote in English or in German other than from that story.
A search for any part of "Man’s religion and metaphysics are the voices of his glands" yields only Tipree's story and works that are referencing or reviewing it.
A similar search for "Religion und Metaphysik des Menschen sind die Stimmen seiner Drüsen" yields only German translations of Tiptree's story.
The Author
There are no references to an author of that name publishing in 1878, other than backtracking to Tiptree's story. The author name just means "nice and wise" (or possibly "A bearer of gifts" in colloquial Austrian) which seems suspicious in itself.