Note 9 — Chapter XI · Disease.
Reading edition
Many ages anterior to this began in India the dread of Ketu, astronomically the ninth planet, mythologically the tail of the demon Rahu, cut in twain as already told (p. 46), supposed to be the prolific source of comets, meteors, and falling stars, also of diseases. From this Ketu or dragon’s tail were born the Arunah Ketavah (Red Ketus or apparitions), and Ketu has become almost another word for disease.9