In Season 1 of TURN: Washington’s Spies in the episode “Against Thy Neighbor,” Captain Simcoe secretly feeds Major Hewlett’s beloved horse, Bucephalus, a poisoned apple. Once Bucephalus ate the apple, he immediately reacted by violently bucking and rearing, and then ultimately collapsed with foam coming out of his mouth. To relieve the horse’s suffering, Captain Hewlett shoots his horse in the head.
This scene got me thinking about what poison(s) existed in the late 18th-century that could have had an immediate and sudden effect on a 1,300 lbs (I am estimating) horse, and be small enough to hide in an apple.
Before I start examining possible poisons Captain Simcoe may have used on Bucephalus, let’s first look at the design of a horse’s stomach. One of the biggest drawbacks to the horse’s digestive system is that it cannot regurgitate anything that enters the stomach. The ability to regurgitate is a body’s defensive mechanism to quickly push out harmful parasites and material, but horses cannot perform this action because of the way their stomachs are designed. The muscles around their lower esophageal sphincter are so strong that they can’t relax enough to let gas and food go back up the esophagus. Once something enters a horse’s stomach, it can only go one way, so a horse needs to be cautious of what it eats. Typically, horses will avoid certain bitter tasting plants that are known to be poisonous or unhealthy. If something tastes very bitter, a horse will usually spit it back out. When my horse injured his knee, I had to give him some bitter tasting anti-inflammatory medication for a week. He refused to eat the medication alone, so I had to mix it with some honey and hide it in his molasses grain for him to eat it.
So what poison could Captain Simcoe have used that was available in the 18th-century that would have immediately harmed the horse, not have a strong bitter taste, and be small enough to disguise in an apple? One possibility is a chemical called strychnine. Strychnine was a popular poison used in the 18th-century mostly to kill rats and other rodents, and sometimes people. Its symptoms included immediate muscle stiffness and then ultimately suffocation because the airway muscles would become paralyzed. However, it would also take a very large dose to kill a horse. Bucephalus did not show these symptoms and the amount of strychnine needed to harm him could not have been disguised in an apple. The possible and the most probable poison used was arsenic. Signs of arsenic poisoning in a large dose are abdominal cramping, diarrhea, vomiting, and then shock. Arsenic does not have a bitter taste and a large dose is small enough that it could have been hidden in an apple. While current horse owners, hopefully, do not need to worry about their horses being intentionally poisoned, horses do die from accidental poisoning by consuming very poisonous plants that can be found near pastures or in gardens. Here are six plants that are common in the United States and can be found in Europe that are highly toxic and can quickly kill a horse.
Water Hemlock - Found near fertile and wet areas. It takes about 2 pounds to kill a horse and can be fatal within 15 minutes of ingesting.
Yew tree - This causes sudden respiratory and cardiac arrest. One mouthful can be fatal. Horses have been found dead with the leaves still in their mouths.
Red maple leaves - The leaves become poisonous when they wilt. Consuming only 1 to 2 pounds can cause kidney and liver failure.
Oleander - Mostly grows in hot climates and planted in gardens. This affects the horse’s heart rate. About 30 to 40 leaves can be fatal.
Foxglove - Grows near forests and meadows and very common in gardens. 3-4 ounces can stop a horse’s heart.
Rhododendron - Typically found in gardens. 1-2 pounds of leaves can lead to cardiac arrest a few hours after consumption.
I am Amy. I love movies, TV, and horses. I grew up with horses and taught kids how to ride during my summer breaks from school. Now I am a country girl living in a city hoping to someday move back into a rural area and own a horse again.