Dear Sir

I have no objection to express my opinion on the subject of vivisection. I detest cruelty, & any physiologist who in investigation causes suffering which can possibly be avoided deserves universal execration.¹

But I am convinced that physiology, which cannot progress without experiments on living animals, is one of the most important of the Sciences, & that it will hereafter confer inestimable benefits on mankind.

Whether or not it has already improved the practice of medicine, is a question of comparative insignificance; for the history of Science shews that benefits to man are generally the indirect result of the search for truth.

It is my firm conviction that he who stops or delays the progress of physiology will hereafter be looked at as the greatest enemy to the sacred cause of true humanity.

If physiologists are reckless in their experiments, which as far as I can discover has not been the case in England, assuredly they ought to be checked & punished by public opinion or the law—

I remain | dear Sir | yours faithfully | Charles Darwin

P.S. It is not probable that you will circulate this letter, but if you do, I appeal to your honour to print the whole of it.—