Since Water for Elephants is set in 1931 (and the present day), there are mini history lessons wrapped up into the story. It is set in the depression and during prohibition. And because of both of those things, I wanted to look up one of the "drinks" to poor circus workers imbibe.
According to Wikipedia (oh yes, that's right, I'm citing a social crowdsourcing medium. My research professor would be so proud.):
"Jake" was not itself dangerous, but the U.S. Treasury Department, which administered the Prohibition laws, recognized its potential as an illicit alcohol source and required changes to discourage drinking. In an effort to trick regulators, bootleggers replaced the ginger solids with a small amount of ginger and either castor oil or molasses.
A pair of amateur chemists and bootleggers, Harry Gross and Max Reisman, worked to develop an alternative adulterant that would pass the tests, but still be somewhat palatable. They settled on a plasticizer, tri-o-tolyl phosphate (also known as tri-ortho cresyl phosphate, TOCP, or Tricresyl phosphate), that was able to pass the Treasury Department's tests but preserved Jake's drinkability.
TOCP was originally thought to be non-toxic; however, it was later determined to be a neurotoxin that causes axonal damage to the nerve cells in the nervous system of human beings, especially those located in the spinal cord.
In 1930, large numbers of Jake users began to lose the use of their hands and feet. Some victims could walk, but they had no control over the muscles which would normally have enabled them to point their toes upward. Therefore, they would raise their feet high with the toes flopping downward, which would touch the pavement first followed by their heels. This very peculiar gait became known as the jake walk and those afflicted were said to have jake leg, jake foot, or jake paralysis.
Within a few months, the TOCP-adulterated Jake was identified as the cause of the paralysis and the contaminated Jake was recovered, but it was too late for many victims. Some users recovered full or partial use of their limbs, but for most, the loss was permanent. The total number of victims was never accurately determined, but is frequently quoted as between 30,000 and 50,000. Many victims were immigrants to the United States and most were poor with little political or social influence.