SECTION VII 



PATHOGENIC PROTOZOA 



FREDERICK F. RUSSELL, M.D. 



INTKODUCTION 



IN the practice of his profession the physician requires a knowl- 

 edge of the pathogenic protozoa found in man and the domestic 

 animals and of their closely related non-pathogenic forms. Quite 

 commonly in the diagnosis of fevers it is necessary to examine the 

 blood of the same patient for both malaria and bacteria, therefore 

 a working knowledge of the principal pathogenic protozoa is essen- 

 tial. In this work it will be possible to describe the forms only of 

 medical interest, and the reader is referred to other works for 

 further information. 



The protozoa are unicellular animal organisms that occur singly 

 or in temporary colonies. The functions of the animals are carried 

 out by the protoplasm of the single cell, parts of which may be 

 differentiated for special purposes and are then called organete. 



CLASSIFICATION OF THE PROTOZOA 



CLASS I. SARCODINA (Rhizopoda) . The body is naked or encased and 

 the animal moves by means of protruding temporary prolongations 

 of the body called pseudopods. They possess one or many nuclei 

 and reproduce by fission or multiplication in a cyst. 

 Order I. Amcebce (Lobosa). Naked or with a simple shell, the 

 pseudopia are lobose or finger-shaped, the nucleus is usually 

 single and there is sometimes a contractile vacuole. Example, 

 the amcebce. 



CLASS II. MASTIGOPHORA (Flagellata). They possess flagella for 

 locomotion and for obtaining food; they may be naked or fur 



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