A great stimulus was given to medicine and surgery when there was applied to these the knowledge gained by Pasteur in his study of fermentation. Pasteur showed that fermentations were chemical alterations in organic matter, excited by the presence of minute organisms very common in the neighbourhood of man. This discovery was applied in the first place to surgery. Lord Lister, then a surgeon in Scotland, showed that the festering of wounds was due to the entrance of minute organisms. Following this clue, he succeeded, by the use of dressings, in preventing the contamination of wounds and at once saw a vast reduction in deaths following surgical operations. Since the discovery of anæsthetics, such as ether, chloroform, and cocaine, and the use of germ-free dressings, surgery has been developed in a marvellous fashion. The varied and delicate feats of abdominal operation are known to all, and recently surgery of the heart has become possible. A comparison of the mortality of the wounded in the different wars of the nineteenth century affords an excellent means of gauging the progress of surgical treatment of gunshot wounds. The mortality of the wounded among the English troops in the Crimean war reached 15.21 per cent.; in the French troops in Italy in 1859–1860, it was 17.36 per cent.; in the German army in 1870–1871, the years in which antiseptic surgery came into use, it fell to 11.07 per cent.; while in the Spanish-American war in 1898, in the most brilliant period of modern surgery, the percentage mortality of wounded had fallen to 6.64.[267] In the recent Transvaal war, the mortality was half what it had been in the Franco-German war.[268] New medical knowledge, founded on the discovery of the nature of ferments and of the virus of infection, has reformed the practice of midwifery to such an extent that puerperal fever, formerly one of the great scourges of humanity, is now extremely rare. Blindness acquired at birth, which formerly rendered many lives extremely miserable, is now practically completely prevented, by means of the precautions taken to hinder the child from being contaminated by the mother in the process of birth. The most successful method is that which was suggested by Credé,[269] a German physician, and consists in placing in the pupils of the infant a minute drop of nitrate of silver, which is an antiseptic, and prevents the occurrence of ocular blennorrhagia. Appendicitis, a disease so common that I referred to it in chap. iv. as one of the most salient examples of disharmony in the human constitution, has been resolutely attacked by medical science. In some cases, surgical interference makes a definite end of the disease; in other cases medical treatment has been enough to subdue the symptoms without recourse to operation.