THE BACILLUS TYPHOSUS.—From what has preceded, it will be seen that the writer is disposed to range himself with those who hold that the exciting cause of typhoid fever is an organized germ, or, in other words, a contagium vivum. Although this view cannot be regarded as positively proven as yet, it has recently received some support through the investigations of Klebs, Eberth of Zurich, and others,42 who believe that they have found in the bodies of those who have died of typhoid fever a micro-organism peculiar to that disease.
42 Klebs (Philadelphia Medical Times, Dec. 3, 1881, from Archiv für experimentelle Pathologie und Pharmakologie, Bd. xiii. H. 5 and 6) claims that he has proved "that there exists in typhoid fever a separate and distinct bacillus—the Bacillus typhosus; that it undergoes certain transformations, consisting at first of little rods and small fine threads, containing a spore in the centre and often at the end, which spores divide off and form new bacilli. It later assumes a larger thread-like form, twisted at the end, and frequently taking a beautiful spiral shape; that the bacilli are observed first in the masses of epithelial cells which accumulate in the alimentary tract or in the air-passages; that they later penetrate the tissues, and are carried along by the blood-vessels and the lymphatics, and form a large network among the tissues they invade; that under a certain procedure, which never causes this same staining in any other living organism or tissue, they appear of a blue color; that they are found only in enteric fever, in which disease every part of the human body is the seat of masses of these bacilli, their quantity corresponding exactly with the severity of the symptoms; and that they produce, when carried into the system of animals, exactly the same disease with the same morbid alterations as in men." He says, further, that "the Bacillus typhosus enters the system by the respiratory passages and by the alimentary canal. This is the cause that in some cases of typhoid fever almost no abdominal symptoms are present, but a low form of pneumonia, developing from the very beginning, so that the lung seems alone to bear the brunt of the disease." He has found these bacilli in greatest numbers in Peyer's patches.
Eberth (British Medical Journal, Nov. 26, 1881, from Virchow's Archiv, Bd. lxxxi. and lxxxiii.) has shown that in typhoid fever the intestinal mucous membrane, the mesenteric glands, and the spleen contain rod bacteria, differing, as he believes, from organisms found in the body in other conditions (among others in phthisis with extensive ulceration of the intestinal mucous membrane). In seventeen cases of typhoid these bacilli were found in six and wanting in eleven. In the six cases the number of bacilli were in inverse proportion to the duration of the disease. They were not found in the spleen in the cases of the longest duration, and only scantily in the mesenteric glands. These bacilli appear not to differ in shape and size from the ordinary rod bacteria, but Eberth believes that they differ from them in their small capacity for taking on the staining of hæmatoxylon, methyl-violet, and Bismarck brown.
Wernich's views (Vjhrschr. f. Off. Geshpfl., xiii. 4, p. 513, 1881) in regard to the nature of the Bacillus typhosus differ from those held by the two authors just quoted. He regards the specific Bacillus typhosus as nothing but the ordinary Bacillus subtilis of the large intestines, which under certain circumstances acquires the power to accommodate itself to the small intestines, to undergo a higher development and to become the exciting cause of disease.
PERIOD OF INCUBATION.—The conditions under which typhoid fever occurs in large cities render it difficult, if not impossible, to arrive at a definite conclusion as to its period of incubation. Occasionally, however, the time which has intervened between the exposure to the cause and the invasion of the disease may be ascertained with precision in the outbreaks which occur in small towns or in isolated country-houses. Under these circumstances it has been found to vary within very wide limits. In the three cases related by Griesinger the attack began the day after exposure to the infection, and in the outbreak at the school at Clapham, referred to by Murchison, twenty out of twenty-two boys were seized with the disease within four days of exposure to the causes. Other instances of a similar character are on record. In cases like the above the rapidity with which the attack follows upon exposure to the cause is no doubt due to the intensity of the poison—a view which is to a certain extent at least supported by the fact that the invasion of the disease under these circumstances is very apt to be abrupt; the attack being often ushered in with vomiting and purging or with grave cerebral symptoms. Sometimes, indeed, the gastro-intestinal symptoms have been so violent as to have given rise to suspicions of criminal or accidental poisoning. In the majority of cases, however, the period of incubation is probably very much longer than in those above referred to. In the outbreak which recently occurred in a farm-house about seven miles distant from Philadelphia, the history of which has already been given in detail, the second case began three weeks after the first, the other six following in rapid succession. In the celebrated epidemic which occurred at Lausen in Switzerland in 1872, and which is referred to by Cayley,43 the first ten patients were attacked within three weeks of the time when the contamination of the spring which supplied the village must have taken place, and these ten cases were followed in the course of nine days by fifty-seven others. In the town of Over Darwen 1500 persons were seized with typhoid fever within three weeks after a patient suffering from this disease was brought to a particular house, the sewage of which was allowed to soak into the ground through which the water-supply pipes of the town passed, and at a point at which they were leaky. Lothholz observed in an epidemic which occurred in the neighborhood of Jena that the average period of incubation was three weeks, the shortest period eighteen days, the longest twenty-eight days. Haegler found in three cases produced by contaminated water a period of at least three weeks.44 There are, however, epidemics on record in which the period of incubation was under two weeks, as, for instance, that of Basle, referred to by Liebermeister, in which a few persons were attacked who had only been in the city from seven to fourteen days. Cayley also refers to localized outbreaks of the disease, as those of Calne and Nunney, in which persons were attacked within fourteen days of their exposure to the cause. C. J. C. Muller of Posen45 says that the average period of incubation of the disease is fourteen days; that it may be not more than ten days, or, on the other hand, as long as from three to four weeks; and that he has known a case in which it was thirty-four days. Murchison believed that it was most commonly about two weeks, and William Budd arrived at the conclusion, from the observation of a large number of cases, that it varied from ten to fourteen days.
43 Brit. Med. Jour., Mar. 15, 1880.
44 Ziemssen's Cyclopædia, vol. i.
45 Neue Beiträge zur Aetologie des Unterleibs-Typhus, Posen, 1878.
From this review of the opinions of various authors the conclusion would seem to be justifiable that the period of incubation in typhoid fever is usually between two and three weeks, but that in many cases it does not exceed ten days, and in rare instances has unquestionably been very much less. On the other hand, there are authentic cases on record in which it is said to have reached, or even exceeded, twenty-eight days. Unfortunately, we do not possess any reliable data with which to decide the question whether it is shorter or longer when the poison is imbibed with the ingesta than when it is inhaled. It would seem, however, that there is a difference in the susceptibility of different individuals to the poison of this disease, in many persons a single exposure to the cause being sufficient to induce an attack, while in others the disease is contracted only after repeated exposure.
MORBID ANATOMY.—As a thorough knowledge of the morbid anatomy of typhoid fever is absolutely necessary to a correct understanding of its pathology, it seems to me better to deviate from the order usually observed in systematic treatises and to proceed at once to a description of the former, rather than to defer it, as it is usual to do, until after the symptomatology of the disease has been discussed.