Complex sentence: In June, Mameli was accidentally injured in his left leg by the bayonet of one of his comrades; the wound was not serious, but an infection took hold, and after a time the leg had to be amputated.
Split into simpler sentences: In June, Mameli was accidentally injured in his left leg by the bayonet of one of his comrades. The wound was not serious, but an infection took hold, and after a time the leg had to be amputated.