14 PRACTICAL PARASITOLOGY 



is yellowish, it points to the presence of alkali. Neutral red may also 

 be employed to distinguish between parasitic Amoebae and leucocytes. 1 



B. SPECIAL. 



Class I. Rhizopoda. 



Order : Amcebina. 



Among the Rhizopods the only true parasites belong to the order 

 Amcebina. It would be a serious oversight, however, to confine our 

 investigations solely to the parasitic members of the group. Many 

 body-cells and this applies especially to the leucocytes are capable 

 of what is known as " amoeboid " movement. Their possession of 

 this power which, as its name shows, is to be regarded as a dis- 

 tinguishing characteristic of true Amoebae, renders it necessary that 

 the student should make himself acquainted with the salient features 

 of the order, as exemplified in the free-living varieties. Only in this 

 way can the knowledge be acquired which will enable him later to 

 distinguish between the true parasit'es and body-cells which have the 

 power of amoeboid movement. 



(a) Free-living Amoebce. 



Conditions under which Amoeba may be Found. If fresh hay or 

 straw is put into a glass receptacle, covered with water, and allowed 

 to stand for a time, numerous Protozoa will develop in the liquid. 

 Among these, the first to attract attention will be the large and very 

 active Infusoria, but Amcebae, though frequently only the smaller 

 forms, will also usually be found. The scum which appears upon 

 the surface of the water, at first as a metallic film but later becoming 

 thick and felty, should be first of all examined. Similar films are 

 seen upon stagnant waters in the open air, and here Amoebae are 

 always to be found. They are also frequently present on the surfaces 

 of the larger water-plants, as, for instance, the submerged portions 

 of the leaves of Stratiotes aloides, or the undersides of the leaves of 

 water-lilies. The larger varieties should Ipe looked for in the vegetable 

 slime of stagnant ponds. Amcebae also occur in mossy tufts and in 

 earth containing much humus (garden soil) ; there is, indeed, one 

 variety which is known as the Amoeba terricola. These organisms will 

 appear if water is poured over the material before examination. 



Cultivation of Amoeba. For anything in the nature of a minute 

 study of the Amcebae, it is of the first importance that the organisms 



1 Cf. S. Prowazek, " Vitalfarbung nrit Neutralrot bei Protozoen," Zeitschr.f. wiss. 

 Zool., vol. Ixiii, 1898, pp. 187-194, and " Zelltatigkeit u. Vitalfarbung," ZooL Anz., 

 vol. xxiv, 1901, pp. 455-460. 



