My own final introductory words of advice are simple: if you want to guarantee you’ll survive running the bulls, stay off the street and watch it from a balcony.

— Alexander Fiske-Harrison, co-author of “Fiesta: How to Survive the Bulls of Pamplona”

MADRID — Ernest Hemingway followed such advice, preferring to write about the traditional running of the bulls, an annual event that these days attracts tens of thousands of tourists from all over the world. So did another devotee, Orson Welles, though it’s hard to resist the thought of the rotund director chugging along with the rampaging animals.

Unfortunately, perhaps, one of Mr. Fiske-Harrison’s co-authors, an American named Bill Hillmann, did not, and was gored in the leg on Wednesday when he tripped during the charge through the streets.

Mr. Hillmann suffered serious muscle tissue damage, but none to the bone or arteries, said Mr. Fiske-Harrison, a British writer and amateur bullfighter who ran behind Mr. Hillmann on Wednesday and later visited him in the hospital.