192 BIOLOGY OF THE PROTOZOA 



Mesnil have shown, human blood serum contains some substance 

 which is fatal to many species of Trypanosoma pathogenic in other 

 mammals, but harmless to Trypanosoma gamhiense, the cause of 

 sleeping sickness. Such protective substances characteristic of 

 natural immunity are developed in the host as a result of infection 

 (acquired immunity) and are fatal to the specific organism causing 

 their formation, or to the toxins produced by the organism. Several 

 such antibodies are demonstrable in the blood serum of the host, 

 after protozoon infection and disease. As shown by experiments of 

 Rabinowitsch and Kempner with Trypanosoma hrucei, Klein and 

 Mollers, with Trypanosoma hrucei, Nocard and Theiler with Babesia, 

 etc. Further evidence is afforded by the formation of agglutinins 

 called out by the presence of Protozoa. Here the results of Roessle 

 with free-living forms of Paramecium and Glavcoma are not con- 

 vincing because of the impossibility of getting these organisms free 

 from l)acteria. With parasitic forms, however, the evidence of the 

 presence of specific agglutinins called forth by infecting parasites 

 is fairly strong. The agglomerations of trypanosomes described by 

 Schaudinn, by Laveran and Mesnil, and others for trypanosomes, 

 are examples of this indirect eft'ect of protozoon secretions. 



Like the hosts with their immunity reactions, so, too, the proto- 

 zoan parasites may develop a resistance to the immunity reactions 

 in the form of a counter-immunity. Thus atoxyl-fast, poison-fast, 

 etc., races of Trypanosoma appeared in Ehrlich's experiments, and 

 many observers with free-living protozoa have shown the acquisition 

 of tolerance towards poisons of dift'erent kinds, e. (/., bichloride of 

 mercury, arsenic, alcohol, etc. 



2. Digestion of Carbohydrates and Fofe.— Specific ferments for 

 the transformation of starch into soluble sugar have not been 

 isolated; nevertheless, the evidence that such action takes place is 

 convincing. Curiously enough, this evidence does not apply to the 

 Infusoria where very little digestion, beyond a slight corroding of 

 starch grains, occurs. In rhizopods, however, especially in the 

 amoeboid Pelomyxa and in species of Amoeba, starch grains are 

 entirely dissolved, according to the observations of Stol^ (1900) who 

 found that the characteristic refringent granules of Pelomyxa 

 palustris have a very definite relation to carbohydrate nutrition. 

 These granules (Glanzkorper) are filled with glycogen, the volume 

 of which increases up to fourfold when the animals are fed with 

 starch, and decreases to entire disappearance when they are starved. 

 Even cellulose is said by Stt)l9 to be digested by this organism and 

 Schaudinn made the same observation on the Foraminiferon Cal- 

 citiiba polymorpha. In Foraminifera generally, according to Jensen, 

 and in myxomycetes, according to Wortmann, Lister and Cela- 

 kowsky, starch may be similarly digested. The flagellates, apart 

 from chlorophyll-bearing forms, apparently have in some cases, at 



