What are the changes Seward notices on Renfield?

Here are some choice excerpts from chapter 8:

Strange and sudden change in Renfield last night. About eight o’clock he began to get excited and sniff about as a dog does when setting. The attendant was struck by his manner, and knowing my interest in him, encouraged him to talk. He is usually respectful to the attendant and at times servile; but to-night, the man tells me, he was quite haughty. Would not condescend to talk with him at all. All he would say was:—

“I don’t want to talk to you: you don’t count now; the Master is at hand.”

For half an hour or more Renfield kept getting excited in greater and greater degree...All at once that shifty look came into his eyes which we always see when a madman has seized an idea, and with it the shifty movement of the head and back which asylum attendants come to know so well. He became quite quiet, and went and sat on the edge of his bed resignedly, and looked into space with lack-lustre eyes. (Chapter 8)