Answer:
Strychnine could cause it because it acts as a poison on the human body and effects the central nervous system. Some of the clinical symtoms are nervousness, restlessness, twitching of the muscles, and stiffness of the neck. In this case, Jan has symptoms like twitching of the muscles and stiffness. Therefore, his systems lead us to believe that the strychnine caused his muscle spasms, twitching, and stiffness.