"Check his pulse" would be said as "vérifiez son pouls"
and "check if he's got lice", "vérifiez s'il a des
poux": it seems hard or impossible for the author to
mix them up.
As someone who learned German as an adult (which also has lots of homophones + gendered nouns etc) I assure you it's not hard to make such mistakes.
I can't edit my parent comment anymore; I didn't mean that it would be hard for anyone to fail to make the distinction, esp. for people beginning to learn French.
But the author has been in France for 15 years and by her own admission, speaks the language pretty well; so I doubt that she actually had a hard time discriminating between "les poux" and "le pouls" -- she probably thought this play on words was funny, but didn't experience the confusion herself.
