When Christiana Edmunds, the Chocolate Cream Killer, began her poisoning spree in April 1871, she chose strychnine as her murder weapon. Strychnine is derived from the seeds and the bark of the nux vomica, a tree found in South East Asia, and is one of the deadliest poisons known to man: 30 mg, for example, is quite enough to kill an adult. Around half of that dosage, 15 mg, is deadly to children.
Considering its toxicity, the Victorians used strychnine for a number of purposes, other than murder. It was a staple ingredient in pest control products and, rather worryingly, was used to make medicine. A number of Victorian physicians hailed strychnine as an effective treatment for a number of conditions, from "nervous disorders" like hysteria, to digestive complaints.
These chocolate-coated strychnine tablets were prescribed for a digestive condition and as you can see from the label, each tablet contains 1/60 of a grain of strychnine (one grain being the equivalent to 64 mg - twice the lethal dose for an adult) so it works out at a daily dose of about 1 mg per tablet. It's not enough to kill you but ingesting strychnine on a daily basis certainly isn't wise!
Coating these tablets in chocolate is not only reminiscent of the Chocolate Cream Killer, it's also indicative of strychnine's wider problem. Its natural taste is so bitter that it makes it almost impossible to (willingly) digest. This was certainly a problem for Christiana Edmunds who, in July 1871, abandoned strychnine and switched to using arsenic, a tasteless and odourless poison - which was far better suited to her murderous spree.
But, sometimes, coating a strychnine tablet in chocolate or another sugary substance made them just a bit too tempting, as shown by this article from 1930:
It's a pretty terrifying thought, that children were helping themselves to strychnine tablets, thanks to the taste of the sugary coating. The symptoms described in this article, like convulsions, are typical of those associated with strychnine poisoning. This is because strychnine works by disrupting the nerve signals between the brain and the muscles. If the brain isn't in full control, the muscles will experience painful spasms and contractions until exhaustion sets in. In severe cases, death can follow in as little as 15 minutes. This goes some way in explaining why Christiana's poisoning spree evoked such terror in Brighton's residents.
I highly recommend J. Buckingham's book, Bitter Nemesis: The Intimate History of Strychnine, to find out more about our relationship with and use of strychnine.