And this is the ultimate lesson that our knowledge of the mode of transmission of typhus has taught us: Man carries on his skin a parasite, the louse. Civilization rids him of it. Should man regress, should he allow himself to resemble a primitive beast, the louse begins to multiply again and treats man as he deserves, as a brute beast. This conclusion would have endeared itself to the warm heart of . My contribution to it makes me feel less unworthy of the honour which you have conferred upon me in his name.