Brieger, Fränkel, Cohen, Sidney Martin, Kanthack, and others, have studied the chemical products of the disease, have obtained them from cultures and from infected tissues, and have been able with these toxins to produce the disease in animals. As with the other infective diseases, so with tetanus, there have been two main lines of researches; the one, toward a fuller knowledge of the chemical changes in the blood and in the central nervous system; the other, toward a fuller knowledge of the nature and ways of the bacillus, and its method of invasion. Before any study of immunity or immunisation, or of neutralisation of the toxins in man by an antitoxin, came the study of the toxins and of the bacillus. It was proved, by an immense quantity of hard work, that the bacillus does not tend to invade the blood, or to pass beyond the lymphatic glands in the immediate neighbourhood of the site of inoculation; that it stays in and about the wound, and there multiplies, and from this site pours into the blood the chemical products which cause the disease; and that these chemical substances have a selective action on certain nerve-cells in the brain and the spinal cord. This is the bare outline of the facts; and no account can be given here of the intricate problems of bacteriology and animal chemistry that have been answered, or are still waiting an answer. At least, it is evident that the whole pathology of tetanus was found, proved, and interpreted by the help of experiments on animals; and that these alone did away with the old false doctrine that the disease was due to rapid extension of inflammation up a nerve to the brain. In 1894 came the use of an antitoxin in cases of the disease, and, in 1895, 42 cases were reported, with 27 recoveries. It cannot be said that any one of the diverse preparations of tetanus-antitoxin, up to this present time, has triumphed over the disease. Tetanus is of all diseases the hardest to reckon with: the first sign of it is the last stage of it; there is no warning, nothing, it may be, but a healed scratch, till the central nervous system is affected with sudden and rapidly advancing degeneration of certain cells. These and other difficulties have stood in the way of an antitoxin treatment; and there is no less difficulty in estimating the efficacy of that treatment. The recovery, under antitoxin, of a "chronic" case cannot always or altogether be attributed to the treatment; and in a very acute case, antitoxin, like everything else, has but small chance of success. Various reports on the antitoxin treatment, published during 1897-1899, give the following figures:-- 26 cases, with 12 recoveries. 98 " 57 " 36 " 25 " 22 " 11 " 51 " 36 " 10 " 7 "