Starring Bertie Wooster and a certain gentleman's gentleman, one Reginald Jeeves.
You can split a line of dialogue mid-sentence with a speech tag, but don't do it too often. It gets precious. Authors generally use this syntactic trick to emphasize the word right before the speech tag, to convey irritation or displeasure, or to slow down the rhythm of the dialogue and make it seem more ponderous or distinct. They can play it straight, allowing them to convey the tone of a character standing on his dignity without wasting extra words on description, or they can use it ironically, for humourous effect. Douglas Adams did this a lot. So did P. G. Wodehouse. The trick is to know where to split the sentence. This is one of those English nooks that is subject to informal convention rather than formal rules, but there are some natural "boundaries" in a sentence which lend themselves to interruption.
You can stick a speech tag after the subject noun:
- I knew Jeeves was still miffed at me the next day when he invaded my sanctum sanctorum at an ungodly hour in the afternoon. "Your Aunt Agatha," he said, to my dismay, "has been to call this morning, Sir."
after the main verb of the sentence (especially when it takes an object):
- "She came, sir," he continued, to my further dismay, "to invite you to dinner this Michaelmas."
after the object:
- "I have taken the liberty," he concluded, to my frantic despair, "of accepting on your behalf."
or after a conjunction:
- "But," I said, "but, but, but Jeeves!"
It can also go between a noun and a phrase that modifies it, such as a prepositional phrase, but not between a noun and its adjective:
- "The person," said Jeeves remorselessly, "of whom to inquire about the dinner is your Aunt Agatha herself."
- "If it is any consolation to you, sir," said Jeeves, "your Aunt Dahlia has agreed to lend Her Ladyship Anatole for the event."
splitting a verb phrase:
- "That does," I said slowly, "put a different light to the thing, Jeeves."
and, interestingly enough, given that you can't split a noun from its adjective, between a verb and its adverb:
- "I suspect you will dine," said Jeeves, "very well."
Notice how stilted the lines sound when you string them all together. No one but Bertie and Jeeves would get away with it, and even then, not in the excess you've seen here. That's why you rarely see it in published fiction unless the author is going for heavy sarcasm or slapstick. Like most verbal gimmicks, it's possible to pull off, but rarely necessary, so don't use it unless you're really, really sure it fits.