Considering how usual it is for leading thinkers to be drawn into controversy, even when most desirous of avoiding it, it is remarkable how little Darwin was mixed up with hotly-debated questions. "I hate controversy," he writes, "and it wastes much time, at least with a man who, like myself, can work for only a short time in a day." One of the few occasions on which he appeared as a champion of a cause was on the question of vivisection, in which a chivalrous feeling led him to intervene with the following letter to Professor Holmgren, of Upsala University, which was published in _The Times_ of April 18, 1881. "I thought it fair," he wrote, "to bear my share of the abuse poured in so atrocious a manner on all physiologists." "DEAR SIR,--In answer to your courteous letter of April 7, I have no objection to express my opinion with respect to the right of experimenting on living animals. I use this latter expression as more correct and comprehensive than that of vivisection. You are at liberty to make any use of this letter which you may think fit, but if published I should wish the whole to appear. I have all my life been a strong advocate for humanity to animals, and have done what I could in my writings to enforce this duty. Several years ago, when the agitation against physiologists commenced in England, it was asserted that inhumanity was here practised, and useless suffering caused to animals; and I was led to think that it might be advisable to have an Act of Parliament on the subject. I then took an active part in trying to get a Bill passed, such as would have removed all just cause of complaint, and at the same time have left physiologists free to pursue their researches--a Bill very different from the Act which has since been passed. It is right to add that the investigation of the matter by a Royal Commission proved that the accusations made against our English physiologists were false. From all that I have heard, however, I fear that in some parts of Europe little regard is paid to the sufferings of animals, and if this be the case I should be glad to hear of legislation against inhumanity in any such country. On the other hand, I know that physiology cannot possibly progress except by means of experiments on living animals, and I feel the deepest conviction that he who retards the progress of physiology commits a crime against mankind. Any one who remembers, as I can, the state of this science half a century ago, must admit that it has made immense progress, and it is now progressing at an ever-increasing rate.