Formerly tetanus was supposed to be due to injury to the nerves, and the idea that it is an infectious disease, due to the introduction of a specific bacillus into a wound, had not been entertained prior to the demonstration that the symptoms which characterise this disease may be produced in the lower animals by inoculating them with garden earth or with a pure

FIG. 12.

Bacillus of tetanus; magnified 1000 diameters. Spores are seen at the ends of some of the bacilli.

culture of the tetanus bacillus. The nervous symptoms are now known to be due to the fact that the tetanus bacillus produces a deadly poison (toxin) which has a special affinity for the nervous tissues. When a barefooted boy steps upon a rusty nail and, as a result of the penetrating wound inflicted by it, develops tetanus, this result is not due to the fact that the nail

was rusty, or that a nerve had been injured, but to the introduction of earth containing the tetanus bacillus, which would more readily adhere to the rough surface of a rusty nail than to a new and clean one. The nature of the wound made is also favourable to infection, as the bruised tissues are not likely to bleed much, and the deep wound with a narrow orifice is well calculated to retain any foreign matter introduced at the time the injury was inflicted. Unlike the various pathogenic bacteria heretofore referred to, the tetanus bacillus will not grow in the presence of oxyIt therefore cannot grow gen. in open wounds exposed to the air, and is incapable of development in the blood of a living animal. It differs in another particular, also, viz., in the formation of

spores," which are developed in the rods - one at the end of each bacillus. These are spherical, highly refractive bodies, which resist desiccation, and may retain their vitality for months and probably for years when present in surface soil or in dust. A temperature of 212° Fahr. is required for their destruction.

When a needle is dipped into a pure culture of the tetanus bacillus, and a mouse is inoculated with it, subcutaneously, the animal falls sick within twentyfour hours and dies of typical tetanus in two or three days. The tetanic symptoms are first developed in

the vicinity of the point of inoculation. In inoculated animals, and in tetanus in man resulting from accidental infection, the bacillus may be obtained in the vicinity of the inoculation wound, but is not present in the blood or in the various organs of the body. The presence of the deadly tetanus toxin may, however, be demonstrated by injecting the blood of a victim of the disease into a mouse, which dies with the characteristic tetanic symptoms after such an inoculation. The fatal dose of this toxin is so small that, according to the Japanese bacteriologist Kitasato, the amount of a culture, from which all living germs have been removed by filtration, which is required to kill a mouse is not more than one hundredthousandth of a cubic centimetre (0.00001 c.c.). The tetanus poison is destroyed by five minutes' exposure to a temperature of 65° C. It is also destroyed by exposure to direct sunlight, but it may be kept indefinitely in a cool dark place. The German chemists, Brieger and Cohn, have obtained the toxin in a precipitated and comparatively pure state, in the form of yellowish transparent scales, which are readily soluble in water. They report that this purified toxin will kill a mouse in the dose of 0.00000005 gram, and they estimate that 0.00023 gram would be a lethal dose for a man. Comparing this with the most deadly vegetable alkaloids known, it is nearly six hundred

times as potent as atropin and one hundred and fifty times as potent as strychnin.

It has long been known that persons who go barefoot are more liable to contract tetanus than those who wear shoes. This is shown by the difference in the mortality between native soldiers and English troops in India. Statistics show that the mortality is higher among males than among females. This, of course, depends upon the fact that they are more outof-doors and are more likely to receive accidental wounds. It is a rather remarkable fact that in the United States more deaths occur from tetanus in cities than in the rural districts. This is no doubt largely due to the considerable number of fatal cases of tetanus which occur among boys as a result of lacerated wounds of the hand made by toy pistols, which are so popular as a means of celebrating Independence Day.

The use of these pistols has now been prohibited by several State Legislatures. Dr. Park of Buffalo, who has given special attention to the subject, reports that in Chicago during the month of July, 1881, sixty cases of tetanus occurred as a result of injuries inflicted by toy pistols. In New York City there were, from the same cause, 38 cases in 1899, 33 cases in 1900, and 27 cases in 1901.

During our Civil War the total number of cases of

tetanus reported, as a complication of gunshot wounds, was 505. This is about one case in every five hundred cases of gunshot injury. The proportion has been much greater in wars conducted by other armies in tropical countries. The total number of deaths from tetanus in the United States during the census year 1900 was 2259, of whom 1516 were males and 743 females. This includes the deaths from "trismus neonatorum "-tetanus of the new-born. Among the poorer classes in southern localities, and especially among the coloured population, tetanus not infrequently results in the new-born from infection. through the navel. In the registration area the highest mortality from tetanus occurred in the States of Vermont and New Jersey. That the mortality reported is chiefly among new-born infants is shown by the fact that of the total number of deaths, 117.7 per 100,000 were among children under one year of age, while the mortality between the ages of five to fourteen was only 3.7, and between fifteen and forty-four only 1.7 per 100,000 of these ages. The victims of the toy pistol are, for the most part, included in the group between the ages of five and fourteen. The deaths below the age of one year, constituting a large share of the total number, may justly be classed as victims of dirt. The number of deaths among the new-born was still