favourable for the growth of bacteria.

The fat looks as fresh and yellow as the day of its removal from the body, and the broth as clear as when it was made. In other tubes of nutrient fluid are portions of subcutaneous tissue, of fascia, of muscle, and of peritoneum, all of which have behaved the same. Had any of the ordinary bacteria been present in these tissues, decomposition would inevitably have ensued. It has been abundantly proved, by the experiments of Pasteur, Lister, Tyndall, and others, that the decomposition of dead organic substances is caused by bacteria. The slight chemical changes which sterile dead organic substances undergo owing to the slow conversion of albumin and fat into other compounds, and owing to crystallisation, need not be taken into account. By some observers whole organs have been preserved entire by simply protecting them from bacterial contamination. Furthermore, it is now a matter of everyday knowledge that milk, vegetables, fruit, and meats of various kinds can be preserved almost indefinitely by destroying the bacteria which may have got into them, and by afterwards protecting them from fresh contamination. Anyone who has worked at experimental pathology soon becomes convinced of the truth of this great induction. Not only can he grow nothing from healthy tissues, but after

successful inoculation with pure cultures of anthrax, tubercle, Staphylococcus aureus, or Streptococcus pyogenes, and so forth, he finds in the tissues the organism he placed there, and none other.

For the success of experiments such as I have mentioned, much depends upon the skill and accuracy of the experimenter, and upon the ease with which the organ can be removed from the body. Some are more easily contaminated than others, and it is particularly difficult to succeed with very hairy animals. Here, again, as the knowledge and skill of experimenters grow, better and more certain results are obtained, and the sterility of the healthy tissues and organs becomes more fully substantiated. The controversy which has ranged around this most important subject reminds one of that which was waged over the theory of spontaneous generation; and there is no doubt but that it is ending in the victory of those who believe in the sterility of the healthy, living tissues. the word healthy! It is not at all improbable but that there are conditions of the body rare indeed, and ill understood, in which clouds, as it were, of bacteria. pass through the circulation. If there be no determining influence, these escape from the body, or are killed within it, without doing any harm. A bruise, a wound, or other locus minoris resistentiæ is, however,

Mark

sufficient to arrest their course and enable them to cause suppuration or other diseases. As I proceed, evidence will be brought in support of this hypothesis; but at present I merely wish to draw attention to the importance of the qualification "healthy." Later, it will be seen how careful we are to avoid any operations, except those of strict necessity, upon patients who are not in perfect health.

DEATH AND PUTREFACTION.

Under ordinary circumstances death is followed by decomposition with such certainty that it is hard to think of these changes apart from one another. It is most important, however, to realise that decomposition does not follow in the footsteps of death, whether it be of the whole body or of a part, unless bacteria are present and able to act. But bacteria are so universal that they attack all dead tissues which are suitable food for them, unless their action is prevented. The bacteria of putrefaction are so universal, that their absence from normal dead tissues may be taken as indicative of the absence of other kinds. I use the words normal tissues, to exclude such as contain tubercle, actinomyces, and other organisms of the same kind.

Putrefaction of albuminous materials was originally thought to be due to a microbe which was called by Cohn the Bacterium termo. Hauser differentiated the B. termo into three species, which he named Proteus vulgaris, P. mirabilis, and P. Zenkeri. He says that these bacteria cause decomposition of wound. secretions, mortification of tissues, and toxic phenomena of greater or less severity. They are pathogenic for rabbits and guinea-pigs. Hauser gave rather massive subcutaneous injections, and produced inflammation, oedema, suppuration, and necrosis. After death the internal organs showed no signs of disease, but P. vulgaris was recovered in pure culture from the peritoneal effusion of a guinea-pig. Cultures of P. vulgaris and of P. mirabilis, which had been sterilised by filtration, caused a rapidly fatal result when injected into the venous system (a true sapræmia). Two facts seem to stand out from Hauser's work-(1) That he used very large doses of his cultures, and (2) that no alterations were seen in the internal organs. An examination of the blood and of the tissues by modern bacteriological methods does not seem to have been made.

1 "Ueber Fäulnissbacterien und deren Beziehungen zur Septicæmie," Leipzig, 1885, S. 12 et seq.

2 Loc. cit., S. 76 et seq.

METHODS OF INVESTIGATION.

FLUID CULTURE

MEDIA.

To test the sterility of small organs, tissues, bits of skin, sponges, towels, silk, fluids, discharges, or substances from wounds, or other materials, transparent fluid culture media are most convenient and speedy. They are more easily prepared than the transparent solid media, and I believe give more reliable results. The following are the ingredients of Hueppe's broth, which is one of the more easily made kinds :1-Boiled water, 1 litre; peptone powder, 5 grms.; grape or cane sugar, 5 grms. ; extract of meat, 30 grms. These are to be mixed together in a glass beaker (with a cover to prevent the unnecessary entrance of dust) and boiled over a gas-burner or spirit-lamp. Whilst boiling, the mixture should be neutralised with a few drops of

a solution of carbonate of soda.

This should be added

until the litmus paper begins to turn blue. After having been boiled for a quarter of an hour, the fluid should be filtered until quite clear, and then decanted into clean and sterile test-tubes, until they are filled

1 Klein, “Micro-organisms and Disease,” third edition, 1896, gives explicit directions for preparing culture media. Also "Practical Bacteriology," Kanthack & Drysdale. London, 1895.