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Rh and others have, however, shown that in the glands and throats of scarlet fever patients a streptococcus, to which is assigned the chief etiological role in connexion with this disease, is present. On the other hand, it is maintained by many observers that these streptococci are nothing more than the streptococci found in puerperal fever, erysipelas, and similar infective conditions, and certainly the organisms described closely resemble Streptococcus pyogenes. In 1904 Mallory described certain " bodies " which he considers may be associated with scarlet fever, and which were sufficiently distinctive to justify him in suggesting that he was dealing with the " various stages in the developmental cycle of a protozoan." These bodies, which were demonstrated in four cases of scarlet fever, " occur in and between the epithelial cells of the epidermis and free in the superficial lymph vessels and spaces of the corium." They are small, varying from the size of a blood platelet to that of a red blood corpuscle, and " stained deUcately but sharply with methylene blue." Well formed rosettes with numerous segments may be seen, forms which MaUory thinks may correspond to the phase of asexual development of the malarial parasite. He also describes " coarsely reticulated forms which may represent stages in sporogony or be due to degeneration of the other forms." He gives beautiful illustrations, both drawings and photographs, of these organisms, and without claiming that he has proved any etiological relation between these bodies and scarlet fever, states that his personal opinion is that such relation exists.

D. — Infective Diseases not yet proved to be due to Micro-organisms.

Small-pox. — ^There have been few recent additions to our knowledge of the aetiology of small-pox, though Dr Monckton Copeman now holds that the smaU-pox organism, like that of vaccine, is probably a very minute bacillus, which, from its behaviour in the presence of glycerin, is possessed of the power of forming spores. If vaccine lymph, taken from the calf, be protected from all extraneous spore bearing organisms and treated with 50 % solution of glycerin, it, in time, becomes absolutely sterile as regards ordinary non-spore bearing organisms. Even the staphylococci and streptococci, usually found in calf lymph, cannot withstand the prolonged action of this substance, but spore bearing organisms still remain alive and active. Moreover, the lymph still retains its power of producing vaccine vesicles, so that the vaccine organism, in its powers of resistance, resembles the spore bearing, and not the non-spore bearing, organisms with which we are acquainted. This vaccine organism must be very minute; it is stated that it can be cultivated only on special media, though it multiplies freely in the superficial cutaneous tissues of the calf, the monkey and the human subject. Perhaps the most important outcome of Dr Monckton Copeman's work on this subject is that he has obtained a vaccine lymph from which are ehminated all streptococci and staphylococci, and, if the lymph be taken with reasonable care, any other organisms which could possibly give rise to untoward results.

Typhus Fever. — Although it is fuUy recognized that typhus must be one of the specific infective fevers brought about by the action of a special micro-organism, no definite information as to the bacterial aetiology of this condition has been obtained. It is always looked upon as a " filth " disease; and from the frequency of minute hemorrhage's, and from the resemblance to the hemorrhagic septicaemia's in other respects, it appears probable that the bacillus of typhus is the organism described by Mott in 1883 as an actively motile dumb-beU coccus, and ten years later by Dubieff and Bruhl as the Diplococcus typhosus exanthematicus; the polar staining and general resemblance to the diplococcus of fowl cholera, the plague bacillus, the diplococcus of " WUdseuche, " certain forms of swine fever and hog cholera, and others of the hemorrhagic septicaemia's, are sufficient to suggest the generic affinity of this organism to this septicaemic group. We have as yet, however (1910), no absolute proof of the etiological relation of the bacillus to this disease.

Measles. — In measles, as in scarlet fever, micro cocci have had ascribed to them the power of setting up the specific disease.

Canon and Pielicke have, however, described minute bacilli somewhat resembling those described as occurring in vaccine lymph. These are found in the blood in the early stages of the disease, and also in the profuse catarrhal secretions so characteristic of this condition. There are no records of the successful inoculation of this minute bacillus, and until such evidence is forthcoming this organism must be looked upon as being an accessory, possibly, but not the prime cause, of measles.

Mumps. — It is generally accepted that mumps is probably caused by a specific micro-organism, the infective material making its way in the first instance through the ducts to the parotid and other sahvary glands. It appears to bring about a peculiar oedematous inflammation of the interstitial tissue of the glands, but slight parenchymatous changes may also be observed. The virus is present in the tissues for some days before there is any manifestation of parotid sweUing, but during this period it is extremely active, and the disease may be readily transmitted from patient to patient. The infectivity continues for some time, probably for nearly a week after naked-eye manifestations of the diseased condition have disappeared.

Whooping-Cottgh. — A diplococcus, a streptococcus, and various higher fungi have in turn been put down as the cause of this disease. It must, from its resemblance to the other specific infective fevers, be considered as an infective disease of microbic origin, which goes through a regular period of incubation and invasion, and in which true nervous lesions, especially of the pneumogastric and superior laryngeal nerves, are somewhat common.

Affanassieff, and later KopUck, have described a minute bacillus, with rounded ends and bi-polar staining, which occurs in the mucus discharged at the end of a paroxysm of whooping cough. KopUck examined sixteen cases, and found this organism in thirteen of them. There can be little doubt that the infective material is contained in the expectoration. It may remain active for a considerable period, but is then usually attached to solid particles. It is not readily carried by the breath, and multiplies specially in the mucous membranes, setting up inflammation, probably through its toxic products, which appear to be absorbed, and, as in the case of the tetanus poison, to travel specially along the lymphatics of the local nerves. Affections of the lung — bronchitis and broncho-pneumonia — may be directly associated with the disease, but it is much more hkely that these affections are the result of secondary infection of tissues already in a weakened condition.

Authorities. — General: AUbutt and Rolleston, System of Medicine (2nd ed., London, 1905 et seq.); Castellani and Chalmers, Manual of Tropical Medicine (London, 1910); Fischer, The Structure and Ftinctions of Bacteria, trans, by K. Coppen Jones (Oxford, 1900); Manson, Sir P., Tropical Diseases (3rd ed., London, 1903); Nuttall, " On the Role of Insects, &c., as carriers in the spread of bacterial and parasitic diseases of man and animals " (Johns Hopkins Hospital Reports, viii., 1899); Schneidemiihl, Lehrb. d. vergleich. Path. u. Therapie d. Menschen u. d. Hausthiere (Leipzig, 1898); Woodhead, Bacteria and their Products (London, 1891). Actinomycosis: Bostrom, Ziegler's Beitr. 2. pathol. Anatomic, Bd. ix. (1891); lUich, Beitrag z. Klinik d. Actinomykose (Vienna, 1892); M'Fadyean, Journ. Compar. Path, and Therap., vol. ii. (1899). Cerebro-Spinal Meningitis: Councilman, Mallory and Wright, Rep. Bd. Health, Mass. (Boston, 1898); E)avis, Journ. Infect. Diseases, iv. 558 (1907); Mackenzie and Martin, Journ. Path, and Bacterial, xii. 539 (1908); Ruppel, Deutsche med. Wochenschr., S. 1366 (1906); Shennan and Ritchie, Journ. Path, and Bacterial, xii. 456 (1908); Symmers and others, Brit. Med. Journ. ii. 1334 (1908). Cholera: Dunbar, in Lubarsch u. Ostertag's Ergebn. d. allg. Pathologie, vol. i. (1896). Diphtheria: Behring, " DieGeschichted. Diphtherie " (Leipzig, 1893), and various other papers, principally in Zeits. f. Hygiene, Bd. xii. (1892) onwards; Ehrlich, " Die Werthbemessung d. Diphtherieheilserums u. d. theoret. Grundlagen, " Klinisches Jahrb., Bd. vi. (1897); Klebs, " Ueber Diphtherie, " Verh. d. II. Congr.f. inn. Med. in Wiesbaden (1883); Loeffler, " Unters. u. d. Bcdeut. d. Mikro-org. f. d. Entst. d. Diphtheritis b. Menschen, &c., " Mitth. a. d. k. Gesundlieitsamte, Bd. ii. (1884); Martin, Sidney, Goulstonian Lectures, Brit. Med. Journ. vol. i. (1892); Nuttall and Graham Smith, The Bacteriology of Diphtheria (Cambridge, 1908); Rouxand Yersin, " Contrib. a T'^tude d. 1. Dipht(5rie, " Annates de I'inst. Pasteur, t. ii.-iv. (1888-1890). Dysentery: Kartulis, " Die Amoebendysenterie, " in KoUe and Wassermann's Handb. d. path. Mikro-org. Ergiinz. Bd. p. 347 (1906); Osier, " On the Amoeba coli in Dysentery