GENERAL PHYSIOLOGY 191 



Notwithstanding the serious diseases in man and mammals 

 generally due to trypanosomes, there is very little positive evidence 

 that secretions are responsible for the effects produced. Experi- 

 ments with extractives from Trj/panosonia hrncel by Kanthak, 

 Durham and Blanford, and by Laveran and Mesnil, gave no 

 indication of toxic effects. On the other hand, Novy and MacNeal, 

 injecting dead Trypanosoma hnicei in guinea-pigs obtained definite 

 fever symptoms, loss of weight and local ulcerations which, however, 

 they did not trace to the effects of a specific toxin. 



Somewhat more positive evidence is accumulating in regard to 

 the possibility of endoenzymes locked up in the trypanosome proto- 

 plasm and liberated on disintegration. Thus a number of observers, 

 amongst whom may be enumerated MacXeal, Plimmer, Leber, 

 Martin and others, have interpreted the rise in temperature of 

 organisms with trypanosomiasis as due to the presence of endotoxins, 

 freed in the blood upon death and disintegration of trypanosomes 

 residting from treatment with medicaments. Also Uhlenhuth, 

 Woithe, Hiibener and others have concluded that endotoxins fatal 

 to rats are liberated if blood containing Trypanosoma equiperdum 

 is first dried, then dissolved again and injected into rats. Schilling, 

 Braun, Teichmann, on the other hand, got no reaction upon injecting 

 dead pathogenic trypanosomes into the peritoneimi or subcuta- 

 neously. 



In all of these cases, with the exception of sarcocystin, the evi- 

 dence in favor of the secretion of exotoxins or the presence of 

 endotoxins, is purely circumstantial and verification by chemical 

 and biological methods with exclusion of other possible contributing 

 factors has not yet appeared. 



Other indirect evidence of the presence of toxins is furnished by 

 the immunity reactions of different hosts in which the presence of 

 antibodies may safely be inferred. In some cases, e. g., coast fever, 

 many babesiases and various experimental trypanosome infections, 

 the first onset may pro\'e fatal. More frec^uently, however, proto- 

 zoan diseases are not fatal at the onset; this is the case with most 

 Trypanosoma, Leishmania and malaria infections in man and experi- 

 mental animals. In rare instances after the onset all parasites in 

 the blood are killed, but in the majority of protozocin diseases many 

 of the parasites escape the reactions of the host and continue to 

 live, either in the blood or in some organ where they are partially 

 protected. These are responsible for the relapses and recurrences 

 characteristic of man\' types of protozoon disease. 



As in bacterial diseases, so here the reactions of the host may be 

 against the parasite (bactericidal), against digestive ferments or 

 against poisonous secretions or toxins. In but few cases, however, 

 are the actual substances and the specificity in^T)lved in such reac- 

 tions, known or recognized. In several instances, as Laveran and 



