The pathogenetic data of Mygale consist of a proving by a young lady and the effect of a bite on a man. In the latter case, inflammation ensued which spread along the lymphatics, violet and afterwards green discoloration; chill followed by fever, dry mouth, and great thirst, trembling, dyspnoea, despondency, and fear of death. The prover developed sadness; dry mouth; nausea with great palpitation, dim sight, and great general weakness; increased flow of urine, hot, scalding, with stinging in urethra. This last symptom has led to the successful use of Myg. in gonorrhoea, chordee, and syphilis. The "trembling" observed in the man suggests its use in nervous cases, but the sphere of Myg. in chorea has been developed from the clinical side. In the cases cured with it, twitching and contractions of facial muscles have been very prominent; convulsive movements of head to right side; twitching of one side of body, mostly right. The twitchings may be so violent as to prevent walking. Limbs are quiet during sleep, movements < in morning. Nausea with strong palpitation should be an indication. Symptoms < by eating. < Sitting (legs in constant motion).