A 45-year-old man incurs blunt chest trauma in a boating accident. On examination he has marked right chest wall pain. A chest radiograph shows a fractured 7th rib on the right side. Over the next 2 days he has subcutaneous soft tissue swelling with nonpainful crepitance on palpation of the right chest wall. Leakage of which of the following is most likely producing this swelling?