in, and purifying the alcoholic precipitate by repeated precipitations from water with absolute alcohol. No peptone was added to the solution. Sidney Martin1 confirmed the work of Roux and Yersin regarding the enzymic nature of the toxine, and also that of Loeffler respecting the precipitation by absolute alcohol. He separated two chemically different substances from the tissues of persons dead of diphtheria, the one an albumose, the other an organic acid. The intravenous injection of the albumose thus obtained caused paralysis, fatty degeneration, and nerve degeneration (Wallerian) in experimental animals, while the intravenous injection of the organic acid produced similar effects in a lesser degree. Sidney Martin concluded that the diphtheria bacillus produced a toxic enzyme capable of digesting (fermenting) the body proteids and setting free an albumose and an organic acid which caused degeneration of nervous tissue. It is possible that the toxine differs from both these bodies, the precipitated albumoses only carrying down the poison mechanically. Roux and Yersin found that an animal injected with increasing but sub-fatal doses of the diphtheria toxine developed immunity both to large doses of the toxine and to injection with the bacillus itself, and this method is now the one adopted in the production of anti-diphtherial serum. The animal, generally a horse, is injected with increasing doses of diphtheria toxine, the toxine being that produced by a specially virulent organism. When the animal shows no rise of temperature, or other reaction to the injection of large doses of toxine, it is bled from one of the neck veins (external jugular) and the blood received into sterile vessels, allowed to clot, the serum syphoned off and 0.5 per cent. carbolic added, to prevent the growth of moulds. The serum is then tested as described in the chapter on immunity. Variations in the Virulence of the Diphtheria Bacillus.-Roux and Yersin found that when the diphtheria bacillus was grown at a high temperature, 39° to 40° C., attenuation of the pathogenic power was brought about; especially was such the case where a current of air was passed over the culture. Where the virulence had fallen by the above treatment it was found that inoculation of animals with the bacilli and streptococci raised the virulence again. Report L. G. B., 1891-2, p. 170. They also found that the organisms obtained from the mouth from time to time during convalescence from an attack of diphtheria, underwent a progressive diminution in virulence, and at the same time a change from the longer to the shorter forms occurred. As a rule the most virulent bacilli are to be found in the most severe cases, but it by no means always follows that the most fatal cases have the most virulent organisms present, the fatality apparently depending considerably upon the resisting power of the individual, as well as the toxicity of the organism. The bacilli may remain present in the mouth for long periods after all clinical signs of the disease disappear and, moreover, frequently retain considerable pathogenic power. Several cases, in which organisms have persisted for upwards of six months, are on record. Those cases in which a nasal discharge persists are generally those in which the bacilli remain the longest. Pseudo-diphtheria Bacillus (Hoffmann's bacillus). An organism often found in cases of simple angina, tonsillitis and various membranous varieties of sore throat, much resembles the true diphtheria bacillus in its cultural peculiarities, but differs in the fact that it is not known to be pathogenic. Certain observers have claimed to have produced a virulent form of this bacillus, in other words, to have turned it into the true diphtheria bacillus by passage through the bodies of susceptible animals, but the evidence is by no means conclusive. Curiously enough the Hoffmann bacillus is generally to be found in the latter stages of diphtheria convalescence, but by no means always. Microscopically it is most difficult to distinguish from the short forms of the Klebs-Loeffler bacillus, and for this and other reasons many authorities are of opinion that it is only a non-pathogenic member of the same species, and that the membranous sore throats associated with this organism are in reality a mild non-toxic variety of diphtheria. The various forms of membranous disease occurring spontaneously in the lower animals are due to other bacteria than the diphtheria bacillus, with the exception of the cat, which has been shown to develop true diphtheria. There are several other bacteria closely allied to the diphtheria bacillus in their microscopical and other characters, as the xerosis bacillus, and at least three varieties which have been isolated from milk.1 1 Eyre, Brit. Med. Congress, 1901. (7) BACILLUS TUBERCULOSIS. Tuberculosis is perhaps the most common disease of men and animals, it is chronic in its course in a large number of cases, and the inflammatory reaction by the body cells to the bacterial invasions has many of the characters of a new growth, so much so in fact that tuberculosis, together with syphilis, actinomycosis and glanders, have been classed by Virchow as "Infective Granulomata." The discovery of the tubercle bacillus by Koch in 1882, and fully described, some two years later, in one of the most classical series of researches in the history of pathology, gave an impetus to the study of bacteriology never since lost. Recently, Koch has stated that the human tubercle bacillus and the organisms affecting cattle are different species and not intercommunicable. The relation of tuberculosis affecting birds to that affecting man has been the subject of considerable research, notably by Nocard, who has come to the conclusion that the two varieties are of the same stock, but the avian bacilli have been modified by their environment. It would be out of place here to enter into a discussion of all the various lesions of the human subject, or of animals with which the tubercle bacillus is found associated; it is, however, necessary in passing to note the frequency of tubercular invasion of the glands, especially in children, and to point out that the mouth may often act as the portal through which the bacilli enter. It may also happen, in fact so far as one can judge often does happen, that the inflammatory conditions set up in the cervical lymphatic glands by the presence of carious teeth provides a point of lowered resistance in the form of an inflamed gland, and that tubercle bacilli circulating in the blood finding such a spot, settle down and develop, and once established, act as the centre of general infection. It is also extremely probable that the specific bacilli themselves make their way in from the mouth, along the tracks of engorged and enlarged lymphatic vessels, much in the same way that the cells of an epithelioma so rapidly spread in oral cancer. The bacilli are not by any means easy to demonstrate in all tubercular lesions, sometimes they are present in large numbers, at other times, as in the discharge from a tubercular sinus, or in the urine of tubercular kidney trouble, they are present only in small numbers and require the most careful search to reveal their presence. I have not been successful in demonstrating tubercle bacilli in carious dentine. Morphology.-Bacilli 2·5—3·5 μ in length, 0·3 μ thick. Longer forms, up to 5 μ, are met with. The rods stain irregularly, giving a jointed, or beaded appearance, so much so that the clear interspaces have been described as spores. At times branched forms are met with, more particularly in the bacilli infecting birds. These branched forms have been described by Hueppe1 and Fischel as indicating that the tubercle bacillus is really the parasitic form of an organism related to the Streptothrix actinomyces. The question of spore formation has not been satisfactorily settled, but the spores, if they exist, are much less resistant than the generality of true endospores. Staining Reactions.-The tubercle bacillus belongs to the series of bacteria known as acid fast," that is, when stained they resist decolourisation, even with strong acids. The tubercle bacillus has an exceptionally resistant sheath, and therefore does not stain by the ordinary methods. The carbol-fuchsine method of ZiehlNeelsen, gives the best results, and is employed as follows: The material to be stained, pus, sputum, centrifugalised deposit, &c. is smeared evenly over the coverslip and the film flamed in the ordinary way. The slip is then placed in the stain for five minutes, kept hot over a water bath. After staining the slip is well washed in methylated spirit, until no more colour is washed out, and then rinsed in water. The slip is now immersed for three seconds in 25 per cent. sulphuric acid, rapidly washed in running water, transferred to carbolic-methylene blue for five seconds, washed, dried and mounted. The bacilli are stained red, the tissue and cells blue. The method is extremely simple, but requires some practice in the decolourising and subsequent double staining. The bacilli stain by Gram's method, but the plasmolysis of the protoplasm gives the appearance of streptococci. Biological Characters.-An äerobic, facultative anäerobic, nonmotile bacillus, only growing at about 37° C. Exposure to steam, at 100° C., destroys the organism in two to five minutes (Schill and Kocher). Exposure to a temperature of 'Loc. cit., p. 43. |