The Protozoa 47 



Penicillium crustaceum (glaucum) is the most common source of 

 contamination of the laboratory media. 



Penicillium minimum, which may be identical with the preceding, 

 was once found in the human ear by Sievenmann. 



THE PROTOZOA 



The Protozoa are unicellular animal organisms as differentiated 

 from the Metazoa which are multicellular animal organisms. The 

 restriction, implied by the term unicellular is, however, too narrow, 

 for there are colonial protozoa that consist of many cells, yet share 

 other protozoan characters. 



For the purposes of this work, however, all protozoa are to be re- 

 garded as unicellular and the individuals independent of one another. 



Classification. — Many schemes have been devised for systematic- 

 ally arranging the protozoa, that which follows being an abbrevia- 

 tion of the standard classification, made to correspond with the 

 requirements of this work that deals only with the pathogenic forms. 



CLASSIFICATION OF THE PATHOGENIC PROTOZOA 



Phylum PROTOZOA (xpuros first, ^oiov animal). Unicellular animal 

 organisms. 

 Class Rhizopoda (pifa root, iruibos foot). Having soft plasmic bodies 

 with or without external protecting shells. The contour subject 

 to change through the formation of extensions known as pseudopods. 

 These may be blunt, rounded, or lobose, filamentous, or anastomosing. 

 The nutrition is holozoic or holophytic. 

 Order Gymnamceba {yviivot naked). Rhizopoda without external 

 shells or coverings. 

 Genus Amoeba [afjalffa to change). 

 Genus Entamoeba. 

 Genus Chlamydophrys. 

 Genus Leydenia. 

 Class Mastigophora (/iao-rtyos whips, (ftopos to bear). Organisms of 

 well-defined form, naked or surrounded by a well-defined membrane. 

 Nutrition is holozoic, holophytic, parasitic, or saprophytic. Mouth, 

 contractile vesicle, and nucleus usually present. 

 Order Flagellata (Latin, fiagellare, to beat). Small organisms with 

 a well-defined mononucleate body, at the anterior end or both ends 

 of which are one or more flagella. Actively motile. May become 

 encysted. Nutrition is holozoic, holophytic, parasitic, or saprophytic. 

 Family Cercomonida. Body pyriform with several anterior flagella 

 and an undulating membrane. 

 Genus Cercomonas. 

 Genus Trichomonas. 

 Genus Monas. 

 Genus Plagiomonas. 

 Family Lambliada. Body pyriform, very much attenuated behind. 

 Ventral surface shows a reniforra depression, about the posterior 

 part of which there are six flagella. There are also two flagella 

 at the posterior extremity. 

 Genus Lamblia (Megastomum). 

 Family TrypanosomidtE. Body delicately fusiform. Contains a 

 nucleus, a blep!" aroplast or centrosome, and an undulating mem- 

 brane. A single wavy flagellum arises in the posterior part 

 of the body close to the centrosome," passes along the edge of the 



