"By Zeus," he said, "I will tell you indeed, Socrates, how it appears to me."
[Reminder: This is Cephalus speaking; he's referring to old age.
The first two words of this sentence are ego and soi; it's as if C. is eager to tell S. his report about old age. The ego is usually unnecessary in Greek and usually indicates emphasis, as I think it does here.
Further, C. swears by Zeus, which is the first instance of that name in the dialogue. S.'s question seems to have really touched off something in C.
(I've reached a new Stephanus page!)]