The recruiting station was inside a railing in the rotunda. A fleet sergeant sat at a desk there, in dress uniform, gaudy as a circus. His chest was loaded with ribbons I couldn’t read. But his right arm was off so short that his tunic had been tailored without any sleeve at all… and, when you came up to the rail, you could see that he had no legs.

[…]

“So they put me out here to discourage you boys. Look at this.” He shoved his chair around to make sure that we could see that he was legless. "Let’s assume that you don’t wind up digging tunnels on Luna or playing human guinea pig for new diseases through sheer lack of talent; suppose we do make a fighting man out of you. Take a look at me — this is what you may buy… if you don’t buy the whole farm and cause your folks to receive a ‘deeply regret’ telegram. Which is more likely, because these days, in training or in combat, there aren’t many wounded. If you buy it at all, they likely throw in a coffin — I’m the rare exception; I was lucky… though maybe you wouldn’t call it luck.”

He paused, then added, "So why don’t you boys go home, go to college, and then go be chemists or insurance brokers or whatever? A term of service isn’t a kiddie camp; it’s either real military service, rough and dangerous even in peacetime . . . or a most unreasonable facsimile thereof. Not a vacation. Not a romantic adventure. Well?”

The guy with no legs is definitely in the book, and he strenuously tries to convince Rico not to join.