There was, however, one political event of his time that called forth Darwin’s keen sympathy and extended comment, and that was the American Civil War. As is well known, English opinion was much divided on this question, and the prejudices of the upper class, at any rate among the more conservative, were in favor of the South. Although Darwin was by no means confident that the North would win, he was strongly on that side from the start, and his numerous letters to Asa Gray show how decided his feeling was. The feeling was not based on the abstract political and constitutional considerations that appealed to Americans, but on Darwin’s rooted, bitter antipathy to the system of slavery in any form. When he was in South America with the Beagle, he had plenty of opportunity to watch the working of human servitude, and it disgusted and repelled him beyond measure. ‘To this day, if I hear a distant scream, it recalls with painful vividness my feelings, when passing a house near Pernambuco, I heard the most pitiable moans, and could not but suspect that some poor slave was being tortured, yet knew that I was as powerless as a child even to remonstrate.... Near Rio de Janeiro I lived opposite to an old lady, who kept screws to crush the fingers of her female slaves. I have stayed in a house where a young household mulatto, daily and hourly, was reviled, beaten, and persecuted enough to break the spirit of the lowest animal.’[324] As a result of these experiences and many others, Darwin imbibed a detestation of slavery and slave-holders which lasted through life, and which led him to oppose them where he could, whether in England or America. The hostility to slavery was based even more deeply on an intense hatred of cruelty, barbarity, and the infliction of physical suffering of any sort. The dislike of such suffering was so keen that from the start it incapacitated Darwin for the medical profession, which his father would have been glad to see him follow. He could not bear the sight of blood, and fled from an operation with disgust. Ill-treatment of animals was especially tormenting to him, and he interfered to prevent it, when he could: ‘He returned one day from his walk pale and faint having seen a horse ill-used, and from the agitation of violently remonstrating with the man.’[325]