Julius Preterius was an human scientist that performed painful and cruel experiments on living cats in order to make a formula to realize a miraculous glue for organic tissue. Many of the cats met by Francis in the first novel, had experienced the traumatic experiments and often lost memory of what happened (or remember only partially): between them there were Joker, Bluebeard and Felicity.
Constant failures led Preterius to maddness, the project's funds were cut and he remained alone. He kept some cats healthy for breeding and having new animals to make experiments (one of them was Jesaia) until one day he seemed to be successful after a test on Claudandus.
(SPOILER): In the most mysterious pages of the story, Preterius (now insane) began to start having closer contacts with Claudandus until to affirm of having heard the cat speaking with him. Claudandus asked him to open the cage and this was the ultimate mistake of the man, before finding the death due Claudandus's assault.