In toxic microbial cultures it is necessary to distinguish the toxins proper from the toxic alkaloids (ptomaines) which generally accompany them; this is easily accomplished by evaporating the solution in a vacuum at about 30°C., and then treating with alcohol and ether, in which the alkaloids are soluble, while the true toxins are insoluble. By fractional precipitation with alcohol it is easy to isolate the peptones and true toxins. The microbial toxins possess two essential properties; one the pyogenic property, thanks to which the toxins first attract, then destroy the white blood corpuscles or leucocytes, and transform them into pus, and the other the pyretogenic property, which appears to belong only quite indirectly to the pyogenic substance. The toxins in general retard the heart action. We will not speak of the distinctions it has been sought to establish between the substances which possess these different properties, but will at once take up the discussion of several of the microbial toxins. =Anthrax Toxin=[100] (from Bacillus Anthracis).--We will describe the preparation of this toxin as a type. [100] ARLOING, CORNEVIN, THOMAS: _Le Charbon Symptomatique_, 1st edit., Paris; and LE DANTEC: _La Bactéridie du Charbon_, Masson, publ.; STRAUS: _Le Charbon des Animaux et de l'Homme_, Paris, 1887. The cultures of the bacillus are made in Liebig's bouillon, to which has been added 0.1% of fibrin, the whole being carefully sterilized for a long time at 110° C. The cultures medium is inoculated with a drop of blood taken from the heart or spleen of an animal that has died of anthrax. At the end of a week, the culture is filtered, and the filtrate acidulated with a little acetic acid and precipitated by adding powdered ammonium sulphate. The flocculent precipitate is collected, washed, dissolved in distilled water, and dialyzed. The dialyzed solution is concentrated in vacuo at 40-45° C., and precipitated by adding to it alcohol. The precipitate formed is then collected and dried.[101] [101] HANKIN: _British Medical Journal_, Oct. 12, 1889, and July 12, 1890. In this manner there is obtained a grayish-white substance which is soluble in water, and which is fatal in large doses, but which, given in repeated small doses, confers immunity against anthrax. According to Hankin, it seems that the toxic property of this toxin is due to an albumose. Marchoux[102] has been able to confer immunity upon sheep by injecting first small quantities of the filtered culture of the anthrax bacilli, and then the virulent anthrax itself. [102] _Annal. Instit. Pasteur_, IX, p. 785. The animals thus rendered immune yield a serum which may be used as a vaccin against anthrax, and which even possesses curative properties under certain conditions.