PART III. SPECIFIC DISEASES OF BACTERIAL ORIGIN. TYPHOID FEVER. Morphology of the Typhoid-bacillus.-The bacillus of typhoid fever was first observed by Koch and Eberth, and grown in pure culture by Gaffky in 1884. Fig. 48.-Bacillus typhi, from an agar-agar culture twenty-four hours old; X 650 (Heim). The typhoid-bacilli are small, plump rods, with rounded extremities (0.5-0.9 X 1-3). In the tissues the organisms lie, as a rule, isolated, while in cultures they are arranged in pairs and not rarely in long filaments. They possess from eight to eighteen terminal and lateral flagella, and, in consequence, they are most actively motile, their movement being serpentine in character. They do not stain so well as other bacteria and they take the stain with some difficulty. It is, therefore, advisable to warm the aqueous staining solutions and also the diluted carbolfuchsin solution. The bacilli do not stain by Gram's method. Spore-formation.-Gaffky considered as spores certain terminal bright, oval bodies that are said to remain unstained. These bodies (polar granules) have, in accordance with subsequent investigations, come to be looked upon as involution-forms. At any rate the bacilli that contain such bodies are not noted especially for their powers of resistance, as they are destroyed with certainty by exposure for ten minutes to a temperature of 60° C. (140° F.). The typhoid-bacillus grows in the absence of oxygen, though by no means so well as in its presence (facultative anaerobiosis). The temperature-optimum for the typhoid-bacillus is that of the body. The organism thrives well, however, at room-temperaThe temperature-maximum is 46° C. (114.8° F.). ture. The Appearance of Typhoid-bacilli in Cultures.The bacillus of typhoid fever-in contrast with most other pathogenic bacteria-exhibits vigorous growth on slightly acid nutrient media. On gelatin-plates deep colonies appear as small, punctate, sharply circumscribed dots; with low powers of the microscope they may exhibit a brownish-yellow color and a whetstone shape. Superficial colonies are much larger, and form a bluish, iridescent, delicate coating, with an irregularly serrated border. Only the central portion of the colony appears, with low powers of the microscope, of a yellowish color, while toward the margin a delicate linear network can be observed, giving rise to a leaflike appearance. The gelatin is not liquefied. In gelatin stab-cultures development takes place along the entire line of inoculation. Superficial growth is pronounced, and presents characteristics similar to those observed in superficial colonies on plates. Gelatin Streak-cultures.-From the center the entire surface of the gelatin is covered by a delicate, iridescent, bluish coating. In all gelatin-cultures a peculiar milky turbidity of the nutrient medium frequently occurs in the neighborhood of the culture. In agar streak-cultures and in blood-serum a whitish coating of inconsiderable density forms, without characteristic peculiarities. The appearance of potato-cultures is of importance. In these the typhoid-bacillus grows in an invisible layer, with an appearance as if nothing at all had developed upon the surface of the potato. If, however, an attempt is made to remove material with a platinum loop, it is at once found that the potato is entirely covered by a layer of some kind. Microscopic examination confirms this observation, and discloses the presence of large numbers of actively motile rods. This mode of development is quite peculiar, and occurs, so far as is as yet known, only with typhoid-bacilli. It is, however, not constant. There are varieties of potato upon which the bacilli of typhoid fever develop in yellowish or brownish, raised, and sharply circumscribed deposits, and generally upon potatoes whose surface yields a neutral or even an alkaline reaction. Such visible growth can be obtained also artificially by rendering the surface to be inoculated of alkaline reaction. Typical characteristic growth takes place only when the potatoes exhibit an acid reaction, which they do, as a rule. In milk the typhoid-bacillus induces slight formation of acid, but never coagulation. In Petruschky's whey (p. 86) the typhoid-bacillus generates not more than three per cent. of acid, whereas the bacterium coli commune generates more than seven per cent. Bouillon is rendered turbid by cultures of the typhoid-bacillus. The typhoid-bacillus does not induce fermentation in nutrient media containing grape-sugar, milk-sugar, or cane-sugar; nor does it form indol in a solution of peptone and sodium chlorid. If potassium nitrite and sulphuric acid are added to peptonecultures, a red coloration does not occur (p. 122, bacterium coli commune). The typhoid-bacillus, as well as the bacterium coli commune and the entire group of bacteria resembling both, is characterized by a certain degree of resistance to carbolic acid, addition of which to the nutrient medium in the proportion of 4 per cent. not inhibiting the bacilli in their growth. Vital Activity of the Typhoid-bacillus.-Typhoidbacilli retain their vitality in sterilized water for a considerable time (up to three months); they may even, at least at first, multiply therein. In unsterilized water they die in the course of two weeks, in consequence of the activity of the water-bacteria, by which they are suppressed, and more quickly in running water than in stagnant water. Under favorable conditions, protected from light, evaporation, and competition, they may persist for a long time. Milk may at times contain living typhoid-bacilli for as long a period as five weeks. In the slime of streams and of wells typhoidbacilli retain their capability of development for not less than three weeks. Buried in the superficial layers of the earth, they have been demonstrated in a living state after five and a half months. They appear also capable of persisting for an equal length of time in the feces for three months and more; naturally only when too many putrefactive bacteria are not present at the same time. Typhoid bacilli bear cold quite well; they are not injured by freezing for two or three times, and subsequent thawing. They are less resistant to heat, as has been mentioned. Spore-formation.) (See Dried in a thin layer, typhoid-bacilli have been found to preserve their vital activity (Uffelmann) In garden-soil for twenty-one days. In sweepings for more than thirty days. In white filter-sand for eighty-two days. Upon linen for from sixty to seventy-two days. According to Kruse, they die in thin layers, dried, within from five to fifteen days. Portals of Infection and Dissemination of Typhoidbacilli.-Dried typhoid-germs may be carried through the air with floor-dust, street-sweepings, particles of clothing, etc. They may, thus, possibly be inhaled. Infection by way of the lungs, however, is rather improbable with regard to typhoid fever, although it played an important part in the earlier theories that denied the transmission from case to case, and considered necessary the presence of the typhoid-bacilli in the earth for their complete maturation; but this has not been demonstrated. Besides, in human beings the digestive tract appears to be the only portal of entry for the typhoid-bacillus. The typhoid-germs must be swallowed, and gain entrance into the intestine. To this end it is necessary that they lodge upon, and be taken up with, food. Apparent infection through the lungs may also be so interpreted that the typhoid-germs contained in dust and with this inhaled are restrained in the upper part of the respiratory tract, to be subsequently carried with food into the digestive tract. It is an important fact that the typhoid-bacillus is not destroyed with certainty by the hydrochloric acid of the gastric juice. The barrier interposed by the stomach thus fails to afford reliable protection against typhoid infection, even when the function of that organ is completely normal. Articles of food may be contaminated with typhoid-bacilli through the intermediation of the air; dust containing typhoid-bacilli may be deposited upon articles of food. More frequent, however, is direct contamination by means of the feces, which become attached to the hands of the at tendants in the emptying of bed-pans, and in the cleansing of soiled linen, and transference to food from want of cleanliness. In this way infection from case to case takes place, as may often enough be demonstrated. The disease occurs in epidemic distribution when a common article of food is contaminated. Thus, epidemics of typhoid fever have been caused by milk, by oysters obtained from infected water, and more frequently by drinking-water. Repeatedly, a communication between wells or sources of water-supply and neighboring cesspools into which undisinfected stools have been emptied has been found to be the cause of typhoid epidemics. In other epidemics contamination of the public water-supply by means of typhoid dejections, or through the washing of infected clothes, has most probably taken place. Recently, typhoid-bacilli have been observed a number of times without a direct relation to cases of typhoid fever being demonstrable or even suspected. Lösener found bacilli that corresponded in all respects with Eberth-Gaff ky bacilli in a specimen of earth obtained from an untilled field, and, further, in the water-supply of Berlin obtained from a conduit in his laboratory. Remlinger and Schneider, using perfect methods, have recently cultivated the same microorganisms from earth, dust, and water. They even found them in the intestines of five individuals who had never suffered from typhoid fever. Observations like these are, however, exceptional, and are as yet beyond explanation. In order that typhoid fever may develop, in addition to the taking up of the bacilli a special predisposition on the part of the individual certainly appears necessary; or the bacilli must possess especial virulence or be taken up in excessive number. In general, human beings may be considered as not particularly susceptible to typhoid fever. The requirement of an especial temporal and local predisposition (elevation of the ground-water), as demanded by the theory that the condition of the soil bears some relation to the occurrence of typhoid fever, can no longer be sustained. The Occurrence of the Bacilli in Typhoid Patients.— The bacilli are found systematically in Peyer's patches, the mesenteric glands, the spleen, the liver, and the bone-marrow of typhoid patients. They are always collected in groups that frequently exhibit a relation with blood-vessels. In |