SECTION VI 



PATHOGENIC PROTOZOA 



FREDERICK F. RUSSELL, M.D. 



INTRODUCTION 



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

 edge of the pathogenic protozoa found in man and the domestic ani- 

 mals and of their closely related non-pathogenic forms. Quite com- 

 monly in the diagnosis of fevers it is necessary to examine the blood 

 of the same patient for both malaria and bacteria, therefore a work- 

 ing knowledge of the principal pathogenic protozoa is essential. 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 infor- 

 mation. 



The protozoa are unicellular animal organisms that occur singly or 

 in temporary colonies. The functions of the animal are carried out by 

 the protoplasm of the single cell, parts of which may be differentiated 

 for special purposes and are then called organella?. 



CLASSIFICATION OF THE PROTOZOA 



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

 the animal moves by means of protruding temporary processes of 

 the body called pseudopods. They possess one or many nuclei 

 and reproduce by fission or multiplication in a cyst. 

 Order I. Amebce (Lobosa}. Naked or with a simple" shell, the pseu- 

 dopia are lobose or finger-shaped, the nucleus is usually single and 

 there is sometimes a contractile vacuole. Example, the amebce. 



CLASS II. MASTIGOPHORA (Flagellata) They possess flagella for 

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

 nished with a membrane ; many forms possess nucleus, contractile 

 vacuole and a small groove spoken of as the cytostome. Ex- 

 amples, the trypanosomes and intestinal flagellates. 



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