The Butler, Treating is Chapter 174 of the Kuroshitsuji manga.
Summary[]
Baldroy is amazed that Ada is so open to show him and Lau the blood drawing room, and wonders what she is thinking. While Baldroy cannot contain his surprise, Ada tells them that the blood drawn here is sent to a research institution to contribute to the advancement of science. In turn, this research institution fully funds Athena Sanatorium as donations, the traditional way of funding sanatoriums, do not cover enough to help the patients sufficiently and help them to return to society.
As Ada talks, Ronald stands silently in the doorsill and takes a look into his Grim Reaper journal.
Surprising Baldroy even further, Ada says that she only allows blood to be drawn from young, physically fit patients who gave her their consent. After all, Ciel told him that the Aurora Society made people unconscious before bleeding them dry. Then, Conny sits up on one of the beds and informs Ada that he is done now. Ada removes his tubing and thanks him for providing half a pint (~236.6ml) of blood this month again. Conny inquires whether this is enough and says that he could give blood every day, but Ada yells at him that she would never allow that as he cannot be healthy if he lacks blood. The effectiveness of bloodletting has been disproven after all. Ada proceeds to say that she wants Conny to eat well and get rest so that he will recover. Conny replies that she worries too much and that he will not get sick at the sanatorium, but Ada insists that she will not allow him to give more blood.
A few more patients announce that they are done, and Ada orders them to get tea and rest before they return to their rooms. When they are gone, she turns to Baldroy and informs him that she will not ask him to give blood as his family donated money to the sanatorium upon his admission. However, she will when his condition has improved enough. Baldroy tells her that he will consider it.
After the tour, Baldroy and Lau talk outside, and Lau remarks that it has been very easy to find out everything they wanted. He also says that he wished this mission would have lasted longer as he wanted to get away from the city for a bit longer. Then, Lau asks Baldroy how they should kill them. Stabbing or shooting them would take too long, so he suggests that they should simply burn the sanatorium down. Baldroy tells him to wait a moment, and Lau wants to know why—after all, the sanatorium "harms the interests of the Earl." Then, Lau inquires why Baldroy came here in the first place.