Dear Sir,

In answer to your courteous letter of April 7^th, I have no objection to express my opinion with respect to the right of experimenting on living animals.² I use this latter expression as more correct and comprehensive than that of vivisection.³ 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 works to enforce this duty. Several years ago when the agitation against physiologists commenced in England, it was asserted that inhumanity was here practiced, and useless suffering caused to animals; and I was led to think that it might be adviseable to have an Act of Parliament on the subject. I then took an active share in trying to get a bill passed, such as would have removed all just causes of complaint, and at the same time have left physiologists free to pursue their researches—a bill very different to the Act which has since been passed.⁴ 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  What improvements in medical practice may be directly attributed to physiological research, is a question which can be properly discussed only by those physiologists and medical practicioners who have studied the history of their subjects; but as far as I can learn, the benefits are already great. However this may be, no one, unless he is grossly ignorant of what science has done for mankind, can entertain any doubt of the incalculable benefits which will hereafter be derived from physiology, not only by man but by the lower animals. Look for instance at Pasteur’s results in modifying the germs of the most malignant diseases, from which, as it so happens, animals will in the first place receive more relief than man.⁵ Let it be remembered how many lives and what a fearful amount of suffering have been saved by the knowledge gained of parasitic worms through the experiments of Virchow and others on living animals.⁶ The future generation will be astonished at the ingratitude shown, at least in England, towards these benefactors of Mankind.

As for myself, permit me to assure you that I honour & shall always honour every one who advances the noble science of Physiology.

I beg leave to remain | Dear Sir | Yours faithfully | Charles Darwin

To | Professor Frithiof Holmgren | Upsala

P.S. Private.—

I have written letters of the same tenour as the enclosed to several of the opponents of experiments on living animals, but they have all been suppressed. It now occurs to me that the publication in England of my answer to you might possibly influence some persons who are not bigoted.— I hope & suppose that you will not object to my doing so, that is if after further reflexion I determine to make the trial; but it is doubtful whether any leading newspaper would publish my letter which would be unpopular.⁷

C. D.—