All Things Bright & Beautiful is the second collection of stories from James Herriot, the Scottish veterinarian and bestselling author.
One of Herriot's cases is the sickeness of Monty, a prize bull, who suffers from fever and refusal to eat. Herriot first diagnoses lead poisoning, but then hits on the idea that Monty has a hairball from licking the other cows. The old vet trick of feeding the bull liquid paraffin has no effect, and Herriot operates, which at the time is a rare occurrence. The hairball comes out and Monty's health improves.
Later, Herriot returns to take a blood sample and discovers that Monty has grown into a huge, violent bull. The farmer restrains Monty, and Herriot collects the blood sample, but Monty pulls free and almost gores him; Herriot escapes at the last second.
Anybody who has travelled a narrow passage a few feet ahead of about a ton of snorting, pounding death will appreciate that I didn't dawdle ... though I was clad in a long oilskin coat and Wellingtons (rubber boots) I doubt weather an Olympic sprinter in full running kit would have bettered my time.
(Herriot, All Things Bright & Beautiful, source Google Books)
The episode is an example of the extreme danger that vets were exposed to on a daily basis. Without the scientific equipment and procedures developed over years of experience -- the sort of experience that Herriot was helping to collect -- many procedures were done on hunch and almost as experiments. In this case, the important failure was of the yoke, which was not designed for a bull's large muscular neck; in the future, yokes were built with an expanding collar that could expand and contract, and were also built out of stronger materials. Today, a bull would be fed a soporific in food before restraint, and the blood would be drawn from outside the pen, through a specialized hatch, so the vet is not at risk.