In every case the acquired immunity is only temporary. We will recall to recollection the method employed by Pasteur for vaccinating against anthrax, using attenuated cultures, a method which is practiced daily at the present time.[103] [103] CHAMBERLAND: _Le Charbon et la Vaccination Charbonneuse_, Paris, 1887. PETERMANN: _Annal. Instit. Pasteur_, VI, p. 32. From the cultures of symptomatic anthrax (Bacillus Chauvæ) Chauvée extracted a very active toxin which can withstand without impairment a temperature of 110°C.[104] Roux[105] has shown that the serum of animals that have succumbed to the symptomatic anthrax is capable of vaccinating against this disease; we have here a new proof that the antitoxin is in fact a product of the defense of the cells of the organism, and the author mentioned has been able to vaccinate guinea-pigs by injecting into the peritoneum culture bouillon sterilized by heating to 115° C. or by filtering through porcelain. [104] DEUTSCHMANN: _Annal. Instit. Pasteur_, VIII, p. 403. [105] _Annal. Inst. Pasteur_, Feb. 1888. =Tubercular Toxin.=--The culture bouillons of Koch's bacillus contain one or more active substances which constitute, and which is at the present designated as, tuberculin.[106] Koch's therapeutic tuberculin is obtained by evaporating to one-tenth its volume a culture bouillon of Koch's tubercle bacilli prepared from a 4-per cent. glycerinic mutton bouillon, and filtering through porcelain. By fractional precipitation it is possible to obtain from the crude tuberculin so prepared a product which is considered as pure tuberculin, and which possesses considerable activity. [106] AUCLAIR: _Thèse de doctorat_, Paris, 1897; and _Arch. de Médecine_, exp. 1898. Prolonged boiling on the water-bath completely destroys the activity of this tuberculin, which moreover hardly ever keeps longer than three weeks. It has been found possible to preserve it for an indefinite period, however, by adding to it 30 to 40 per cent. of glycerin. It possesses all the general reactions of albuminoids. Tuberculin is not toxic in the proper sense of the word. Injected in small quantities into the healthy human being[107] and into healthy animals, it exerts no effect; on the other hand, however, in tubercular organisms, even in incipient stages of the disease, even where it is almost impossible to make a clinical diagnosis, the injection of very small quantities develops a lively and characteristic reaction.[108] [107] KOCH: _Deutsch. Med. Woch._, Nov. 13, 1890-1897, No. 14, p. 209. [108] _Annal. de l'Instit. Pasteur_, V, p. 191; _Arch. de la Soc. Biol. de Saint-Pétersbourg_, I, p. 213. Grasset and Vedel consider the tuberculin as an excellent means of diagnosing tuberculosis in man, but in such a case it is necessary to operate with the greatest caution, with very small quantities of the tuberculin, and to feel, in some sort, the sensitiveness of the patient, particularly in the case of children.