"I know how I've got to do it.

I have to make my own medicine--and take it.
You say John Sibley is vicious.

He has only got one vice." "Isn't it enough?
Gambling--" "That isn't a vice; it's a sport.

It's the same as Mr.Crozier had.
Mr.Crozier did it with horses only, the other does it with cards and horses.

The only vice John Sibley's got is me." "Is you ?" asked her mother bewilderedly.
"Well, when you've got an idea you can't control and it makes you its slave, it's a vice.