Why does Matthew change his mind about allowing Bulkeley into the house?

In Chapter 15, Judith comes down with a fever. At first, everyone thinks it is just moping. Soon, the fever begins to affect more of the townspeople. The fever affects mainly children and young people. With Judith sick, Kit takes on a larger burden of work. She, herself, becomes ill, but as she is strong and healthy, she soon recovers. Mercy, though, comes down very ill. Her fever will not let up. Rachel and Kit care for her day and night, to no avail. At first, Matthew does not want to accept Dr. Bulkely's help, because he is a royalist. When Bulkely appears on the doorstep offering to help, Matthew gives in gratefully.