From: Blue Latitudes: Boldly Going Where Captain Cook Has Gone Before, by Tony Horwitz (Picador, 2002), pp. 218-219:
Cook resumed his polar probe during the next southern summer , after wintering in Polynesia. The second approach to Antarctica proved even more wretched than the first. Livestock perished, tropical provisions ran out, and the men—eating little except weevil-ridden biscuits and salt rations—began to show signs of scurvy and depression.
“Salt Beef & pork, without vegetables for 14 weeks running, would probably cure a Glutton, even in England,” wrote William Wales, the ship’s astronomer. According to George Forster, even the resilient Cook became “pale and lean, entirely lost his appetite, and laboured under a perpetual costiveness [constipation].”…
Three weeks later, Cook collapsed. He doesn’t reveal much about this in his journal, except to note that he was confined to his cot for a week because of a gastric affliction he called “Billious colick.” George Forster makes it clear that the captain’s condition was much graver than Cook suggests. The captain suffered from “violent pains” and “violent vomiting,” Forster wrote. “His life was entirely despaired of.”
The treatment given Cook—opiates, clysters (suppositories), plasters on his stomach, “purges” and emetics to induce vomiting—probably didn’t help. When Cook finally recovered, his first meal in a week was the only fresh meat on the ship: the Forsters’ dog. “Thus I received nourishment and strength from food which would have made most people in Europe sick,” Cook wrote.