Final answer:
Mrs. Schachter's insanity may have been caused by a combination of personal and external factors.
Step-by-step explanation:
In the case of Mrs. Schachter going insane, there are several factors that have contributed to her condition. In the first passage, it seems that Jane's troubles and the loss of her herd could have led to her mental instability. Similarly, in the second passage, the undiagnosed disease of Lady Madeline ultimately causes her to go insane. In the fourth passage, the jealousy and torment experienced by McTeague due to his pursuit of Trina may have played a role in his deterioration.