254 PATHOGENIC BACTERIA. researches of J. H. Wrightl are in accord with those of Tedeschi rather than with those of Baumgarteii, for Wright observed first a marked degenerative effect upon the tissue, and then an inflammatory exudation amount- ing in some cases to actual suppuration. As has been mentioned, cultures of the bacillus lose their virulence more or less after four or five generations in artificial media. While this is true, attempts to atten- uate fresh cultures by heat, etc. have so far failed. Leo has pointed out that white rats, which are immune to the disease, may be made susceptible by feeding with phloridzin and causing a glycosuria. Kalning, Preusse, Pearson, and others have pre- pared a substance, "mallein," from cultures of the bacillus, and suggested its employment for diagnostic purposes. It seems to be quite useful in veterinary medicine, the reaction occasioned by its injection being similar to that caused by the injection of tuberculin in tuberculous patients. The manufacture of mallein is not attended with great difficulty. The bacilli are grown in glycerin bouillon for several weeks, killed by heat, the culture filtered through porcelain and evaporated to one- tenth of its volume. It has also been prepared from potato cultures, which are said to produce a stronger toxin, A febrile reaction of more than 1.5° C. following the injection is said to be specific of the disease. Babes has asserted that the injection of this toxic product into susceptible animals will protect them from the disease. Various experiments have been made with curative objects in view. Certain observers claim to have seen good results follow the injection of mallein in repeated small doses. Others, as Chenot and Picq, find the blood- serum from immune animals like the ox to be curative when injected into infected guinea-pigs. 1 Jour, of Exp. Med,9 vol. L, No. 4, p. 577.