that the Micrococcus melitensis might similarly be “stored”
in an animal which might show but slight, if any, manifestations
of Malta fever. Indications as to the direction in which to
look were given in the following fashion. There was a strike
amongst the dairymen supplying the barracks in Malta and it
became necessary to replace the goat’s milk in the dietary of
the troops by condensed milk. What followed? In the first
half of the year 1906 there had been 144 cases (in 1905 there had
been 750 cases), in the second half after the alteration of the
milk supply, only 32 cases were recorded and in 1907, 7 cases
during the whole year. In the navy during the same period
there were, in 1905, 498 cases, in 1906, 248 cases and, from
January to September 1907, not a single case.
The most common method of infection is by the ingestion of milk, but the milk when handled may also give rise to infection through finding its way into cuts, bruises, &c. In the goat the disease is of an extremely mild character, the clinical symptoms, which are present for two or three days only, being easily overlooked. In spite of this the goat is highly susceptible to the infection either by the various methods of inoculation or as the result of feeding with contaminated or infected material. The micrococcus is often found in the circulating blood from which it may be excreted along with the urine and faeces. In time, however, it disappears, first from the general circulation and most of the viscera, persisting longest in the spleen, kidneys and lymphatic glands. In the later stages of the disease the micrococcus is found in the milk even after it has disappeared from the above glands. It is during this stage that the milk of the goat is so dangerous, as now and again it may contain an enormous number of the specific micrococcus varying “within wide limits from day to day,” although bearing “no relationship to the severity of the infection, air temperature, &c.; the presence of the Micrococcus melitensis in the milk appears to be merely the result of a mechanical flushing of the mammary glands by means of which the cocci multiplying therein are removed.” As pointed out by the Mediterranean Fever Commission the micrococcus of Malta fever from its vantage ground in the milk may make its way to ordinary ice-creams and to native cheeses, in which it appears to retain its full virulence. Monkeys are especially susceptible to this disease, contracting it readily when they are fed with milk from an infected goat. In 1905 an interesting experiment was, unintentionally, carried out. An official of the United States Bureau of Animal Industry visiting Malta in the summer of that year purchased a herd of 61 milch-goats and four billy goats. These were shipped via Antwerp to the United States. On arrival at Antwerp the goats were transferred to a quarantine station, where they remained for five days and were then consigned by steamer to New York. On board the SS. “Joshua Nicholson,” which took the goats from Malta to Antwerp, were twenty-three officers and men; ten out of the twenty-three were afterwards traced. One was found to have been infected by M. melitensis at an unknown date, and eight had subsequently suffered from febrile attacks, five yielding conclusive evidence of infection by M. melitensis. It is interesting to note, however, that two men who boiled the milk before drinking it, and an officer and a cabin-boy who disliked the milk and did not drink it at all, came off scot free.
These cases taken by themselves might leave the question somewhat open, as there was a possibility that the men attacked might have been in contact with infected patients in Malta. A far more conclusive case was the following. A woman at the quarantine station at Athenia, N.J., U.S.A., who partook freely of the mixed milk from several goats, over a considerable period, suffered from a typical attack of Mediterranean fever some nine or ten weeks after the goats had been landed in America. In this case “contact” with and other modes of exposure to infection by human patients could all be eliminated.
It may be held then that the M. melitensis leads a more or less passive existence in the body of the Maltese goat, only exercising its full pathogenic action when it gains entrance to the human body. There is some slight evidence that the Micrococcus melitensis may remain alive with its virulence unimpaired even when taken up by the mosquitoes Acartomyia and Stegomyia, and again in the common blood-sucking fly, Stomoxys, for a short period, four or five days. It can be recovered for a longer period and still in a fairly virulent condition from the excreta of these insects. In spite of this, transmission of the disease by these insects, though apparently possible, does not appear to be of very frequent occurrence. Inoculation with a vaccine prepared from the Micrococcus melitensis appears to exert a protective influence for a period of about four months, after which time there is a marked diminution in the immunity conferred by this vaccination.
Relapsing Fever.—The specific cause of relapsing fever (famine fever) appears to be the Spirillum Obermeieri, an organism which occurs in the blood (during the febrile stages) of patients suffering from this disease. Between the febrile stages are periods of intermission, during which the spirillum disappears from the blood and, apparently, retires to the spleen. This disease, in epidemic form, follows in the footsteps of famine and destitution, specially affecting young people between the ages of fifteen and twenty; it seldom attacks children under five years of age, but when it attacks patients over thirty it assumes a very virulent form. In monkeys inoculated with blood containing the Spirillum Obermeieri the first symptoms appear between the second and sixth days. In the human subject this incubation period may last as long as three weeks; then comes an attack of fever, which continues for about a week, and is followed by a similar period of apparent convalescence, on which ensues a pyrexial relapse, continuing about half as long as the first. The spirilla, the cause of this disease, are fine spirals with pointed ends, three or four times as long as the diameter of a red blood corpuscle. Although it has as yet been found impossible to cultivate these spirilla outside the body, human beings, and monkeys injected with blood containing them, contract the disease; and in monkeys it has been found that during the period before the relapse the spirilla have made their way into the cells of the spleen. As yet little is known as to the mode of development of these organisms, and of the method of their transmission from one patient to another, but it is thought that, as in the case of malaria and the tsetse-fly disease, they may be carried by bloodsucking insects. Relapsing fever is distinguished from typhoid fever by its sudden onset, and by the distinct intermissions; and from influenza by the enlargement of the spleen and liver. The most satisfactory method of diagnosis is the examination of the blood for the presence of the spirillum during the febrile stage. The post-mortem appearances are those of a toxic (bacterial) poisoning. Curious infarction-like masses, in which are numerous spirilla, are found in the spleen; in the liver there is evidence of acute interstitial hepatitis, with cloudy swelling of the liver cells; and similar changes occur in the kidney. Fatty degeneration of the heart and voluntary muscles may also be met with.
Plague.—During recent years opportunities for the study of plague have unfortunately been only too numerous. In patients suffering from this disease, a micro-organism, capable of leading either a saprophytic life or a parasitic existence in the human body, and in some of the lower animals, was described independently by Kitasato and Lowson and by Yersin, 1894, in Hong-Kong. It is a short moderately thick oval bacillus, with rounded ends, which stain deeply, leaving a clear band in the centre (see Plate II., fig. 7). It thus resembles the short diphtheria bacillus and the influenza bacillus. Certain other forms are met with—long rods and “large oval bacilli, pear-shaped or round, imperfectly stained pale involution forms”—but the above is the most characteristic. It grows readily on most media at the temperature of the body, but, like the glanders bacillus, soon loses its virulence in cultivations. It may be obtained in pure cultures from the lymph glands, and from the abscesses that are formed in the groin or other positions in which the glands become enlarged and softened. It may also be found in the spleen and in the blood, and, in the case of patients suffering from the pneumonic form of the disease, even in the lungs and in the sputum. It has also been found in the faeces and urine. (It is very important that these excretions from plague patients should always be most carefully disinfected.) This organism, when obtained in pure culture and inoculated into rats, mice, guinea-pigs or rabbits, produces exactly the same symptoms as does material taken fresh from the softened glands. The symptoms are local swelling, enlargement and softening of the lymphatic glands, and high fever.
The difficulty of explaining the spread of plague, at one time apparently almost insuperable, has at last been overcome, as it has been found that although the acute pneumonic plague is undoubtedly highly contagious, the spread of the bubonic and septicaemic forms could not be explained on the same hypothesis. As the pneumonic form is met with in only about 2·5% of the whole of the cases, transmission by direct contagion seems to be an utterly inadequate explanation. In the autumn of 1896, when the plague broke out in India, and those dealing
