I believe that most sensible people feel as Mr. Darwin felt, and I myself would certainly subscribe to what he wrote to me in the letter which I have quoted above. Amongst those who feel thus strongly on the subject there are some who can control their emotion and calmly consider whether the pain inflicted under any given circumstances is justifiable as leading to a great ultimate diminution of pain by the knowledge obtained. There are others who are constitutionally incapable of controlling their emotion in this matter. They hear dreadful stories of cruelty, and are so upset that they are incapable of ascertaining whether the stories are true or not. They are quite unfit to weigh the question as to whether the pain given in the case they hear of may or may not be a necessary step towards avoiding far greater pain in the future for thousands of human beings and sentient animals. Far be it from me to think harshly of these tender-hearted people, though their mistaken outcry may tend to stop the discovery of pain-saving and life-saving knowledge. I feel more sympathy with them than with those (happily rare) individuals who are really indifferent to seeing or giving bodily pain to men or to animals. There is reason to hope that careful and well-considered statement of the facts will eventually enable many of those who are mentally unhinged by descriptions of pain and bloodshed to recognise that they have been deceived, partly by their own fancies and partly by the false statements of professional agitators. Unfortunately, there are always present in human society individuals who find it to their advantage to excite the minds of their more emotional fellow-citizens by tales of horror. The lust of such power--the power to lead or urge a large body of men driven by emotional excitement into violent action--has led from time to time to exaggeration, misrepresentation, and elaborate plot and perjury directed against a group of innocent or worthy people, whose proceedings were mysterious or misunderstood by the community at large. Thus, from time to time, the crowd has been infuriated and led to the murder of the Jews by agitators, who started the baseless story that the Jews had slain a Christian child, and used its blood at their feast of the Passover. Titus Oates and Lord George Gordon made use of the unreasoning emotion of the crowd in the same way. To a less serious extent the emotional unreasonableness of a number of men and women is being played upon at the present day by quite a large variety of agitators, would-be leaders of crusades and campaigns against the beneficent work of the physiological and medical laboratories of our universities and medical schools.