868 IMMUNOLOGY 



Rouget (1896) first found that the serum of rabbits and dogs, which 

 had been infected with T. equiperdum and had become cachetic, exerted 

 a protective action, in a dose of 0.3 cc, on mice infected with the pass- 

 age strain as measured by the survival time of the mice. The fact that 

 immune serum is protective led Laveran and Mesnil (1901) to hope 

 that serotherapy might possibly be developed against pathogenic trypano- 

 somiasis, but so far this hope has not materialized. Schilling (1902) 

 was the first to recognize the phenomenon of trypanolysis in vitro. 

 Rodet and Vallet (1906) studied the lysins systematically, and Massag- 

 lia (1907) showed that the trypanosomes which repopulate the blood 

 after each trypanolytic crisis are immunologically different from the 

 original strain and are resistant to the lysin producing the crisis. Thus 

 serum from an infected guinea pig before a crisis is only slightly lytic, 

 whereas that during and after the crisis is strongly lytic to the original 

 strain of trypanosomes, but has no deleterious effect on the trypano- 

 somes reappearing after the crisis. Levaditi and Mutermilch (1909) 

 reported that the lysis is a complement-amboceptor reaction (i.e., in- 

 volves a heat labile component of serum and the heat stable antibody), 

 and Leger and Ringenbach (1911 and 1912) found a group specificity 

 between trypanolytic immune serums and different species of pathogenic 

 trypanosomes. 



W, H. Taliaferro and T. L. Johnson (1926), in a study of the pro- 

 duction of artificial crises (Figure 193) by immune serum against T. 

 equinum in mice, found that zones of inhibition may occur. T. L. John- 

 son (1929), in a continuation of this work, found that the production 

 of the artificial crisis, with resulting lengthening of life in the mouse, 

 is dependent not only upon the amount of immune serum, but upon 

 the absolute number of parasites present and upon the strain of para- 

 site used. For example, when a given serum was injected into mice 

 whose blood showed one to five parasites of a particular strain per 

 microscopic field, it caused lysis of the trypanosomes uniformly in all 

 doses greater than the minimal effective dose; when injected into mice 

 the blood of which contained from ten to twenty-eight parasites of the 

 same strain per microscopic field, it caused alternate zones of lysis and 

 non-lysis (zone phenomenon); whereas when injected into mice whose 

 blood showed fifty parasites per microscopic field, no lysis occurred, 

 no matter what dose of serum was given. Moreover, Johnson was able 



