http://sunny.crk.umn.edu/courses/biolknut/1020/micro4/sld006.htm In the early 1900s, Paul Ehrlich recognized that certain dyes stained micro-organisms but not the animal cells. By using this concept of "selective toxicity," Ehrlich discovered that an arsenic-containing drug would inhibit Treponema (causative microbe of syphilis). He named the drug Salvarsan because it was a salvation against syphilis and contained arsenic.
There's another thread on the origin of the song Pills of White Mercury, which were also used as a treatment.
Tricks may be the missing word, although it doesn't seem to fit the context completely. There again, it may have been a slang word familiar at the time. Perhaps it is something closer to pills, drugs or treatment?