“Excuse the freedom which I have taken in addressing you, on the grounds of our common love for science, and believe in the profound esteem of yours, very sincerely, JOSEPH LISTER.” The wad dressing of Dr. Alphonse Guérin, surgeon at the Hôtel-Dieu, Paris, which has already rendered great assistance to surgery, and has been the subject of a very favourable report at the Academy of Sciences in Paris, was invented by its author in consequence of certain reflections suggested to him by the perusal of our researches. The commission which framed the report made, through M. Gosselin, some wise reservations in the case of certain theoretical ideas which M. Guérin had not sufficiently proved by experiment. We have no doubt, however, that when the matter is thoroughly examined, facts will confirm the truth of the wide views entertained by the surgeon of the Hôtel-Dieu. Dr. Déclat has founded quite a new system for the treatment of infectious diseases, which is based upon the use of one of the best known antiseptics, phenic acid. His theory, which he affirms was suggested to him by our studies on fermentations, is, that the diseases which transmit themselves are, each of them, the product of a special ferment, and that both medical and surgical professors of therapeutics should make it their study to prevent exterior ferments from penetrating into the liquids of our economy, or in the event of these ferments having found their way into the system, to discover _antiferments_ for their destruction, without effecting any change in the vitality of the histological elements of the liquid or tissues. There is no doubt that extreme caution must be exercised in dealing with questions of this kind, as M. Sédillot has authoritatively remarked; but at the same time it cannot be denied that the more such questions are discussed with exactness, the more those celebrated practitioners who originated them are confirmed in the ideas which first guided them. We may give another example of this. In 1874, in consequence of a communication addressed to the Academy of Sciences by Messrs Gosselin and A. Robin, on the subject of ammoniacal urine, we made the observation that we should endeavour to ascertain if, in all such cases, the urinary fluids were not rendered ammoniacal by the presence of the little ferment of the urea, which we have previously noticed,[27] and which has since then been discussed with remarkable intelligence by M. Van Tieghem, in the thesis which he maintained for his doctor’s degree. The suggestion and the considerations that justified it led to a discussion before the Academy of Medicine, in which contrary opinions were maintained. We lost no time in submitting these to the test of facts. We could not find a single person suffering from ammoniacal urine, in whose case the little ferment which we mentioned was not to be detected. Our predictions were thus completely justified.