What is odd about Mrs. Dubose's behavior each afternoon when Scout and Jem vist her?

As time passes, the old woman stops speaking and her mouth opens and closes while her head sways from side to side. Jem asks her if she is all right, but she doesn't reply. In a few minutes, an alarm clock sounds, and Mrs. Dubose's assistant shoes them out of the room and tells them to go home because it is time for Mrs. Dubose's medicine. This same sequence of events happens every time Scout and Jem go to Mrs. Dubose's house.