S. bronchialis is a species distinct from the spirochætes occurring in the mouth. It differs from them in morphology, pathogenicity and in staining reactions. It is not a developmental form of any bacterium, and is an entity in itself.
The passage from man to man is effected most probably by means of spirochætes, and especially coccoid bodies, that leave the body in the spray with expired air and by way of the nasal secretions. Owing to the fragility and short life of S. bronchialis extracorporeally, the resistant coccoid bodies in air, in dried sputum and dust, and possibly also on the bodies of flies and other insects, are probably instrumental in inducing attacks of bronchial spirochætosis in human beings, especially those having a lowered bodily resistance, such as occurs after a chill. Lurie (December, 1915), has described a case from Serbia.
The Spirochætes of the Human Mouth (see p. [122]).—Two species of spirochætes were recorded as occurring in the human mouth about forty or fifty years ago. These are Spirochæta buccalis, Steinberg (often ascribed to Cohn, 1875), and S. dentium, Miller (often attributed to Koch, 1877).
The most recent work on S. dentium and S. buccalis is that of Fantham[1267] (July, 1915), who observed the parasites ascribed to Cohn and to Koch, these being the two common spirochætes seen in the mouths of natives of the Sudan and of Europeans in England, as well as the forms described and cultivated by recent investigators. Some of the mouth spirochætes are not very active, but there is marked corkscrew and boring movement, and they are flexible. Tangles or tomenta of these mouth spirochætes are common. Internal structure is seen with some difficulty, but in some specimens it can be determined, and chromatin granules are then seen. Mühlens (1907) figured stained specimens of S. buccalis and S. dentium, in which chromatin-coloured granules were distributed along the bodies of the organisms.
S. dentium has tapering ends, and varies in length from 4 µ to 10 µ. S. dentium is rather like Treponema pallidum, and has been placed by some workers—for example, Dobell—in the genus Treponema. It has already been mentioned, on p. [128], that Noguchi cultivated three species of Treponema from the human mouth—namely, T. macrodentium, T. microdentium, and T. mucosum, but they cannot be easily distinguished morphologically, and so may appear to be biological varieties of S. dentium.
S. buccalis has somewhat rounded or bluntly acuminate ends and varies in length from 9 µ to 22 µ. A slight membrane or crest may sometimes be observed. S. buccalis was found to be the predominant spirochæte in the mouths of eight natives examined by Fantham in the Anglo-Egyptian Sudan.
S. buccalis and S. dentium take up stains well and with relative ease. Intracellular stages of the parasites are uncommon. Multiplication by binary fission has also been observed. Coccoid bodies or granule stages of the mouth spirochætes are formed, but appear to be relatively few in number.
J. G. and D. Thomson[1268] (1914) have written an interesting paper on various spirochætes occurring in the alimentary tract of man and of some of the lower animals. They have also given a useful list of references, and the work of some of the earlier authors is discussed in the paper.
With regard to the general morphology of spirochætes, it may be noted that the so-called axial fibre of Zuelzer is acknowledged to be homologous with the membrane or crista of molluscan spirochætes.
Coccidia in Cattle.—Regarding the remarks on coccidiosis or “red dysentery” in cattle on p. [147], it may be added that Schultz[1269] (July, 1915) has found the malady among cattle in the Philippine Islands. He states that some irregular or atypical cases of apparent rinderpest are really due to coccidia. As has been pointed out by Montgomery, rinderpest can be transmitted by blood inoculation, while coccidiosis cannot be so transmitted, but may be diagnosed by the microscope. These differences should be remembered as the two diseases are often found to be associated and are difficult to separate clinically. Coccidia have also been found in Australian cattle.