THE ANIMAL PARASITES OF MAN. 



MAN is one of those organisms in or on which a whole host of parasites find 

 conditions suitable for their existence : Protozoa, Platyhelminthes, Nematoda, 

 Acanthocephala, Hirudinea, and a large number of Arthropoda (Arachnida as well 

 as Insects) all include members which are parasites of man. These animals either 

 live on the external surface of the body or within the intestine and its appendages. 

 Other organs and systems are not quite free from foreign organisms we are 

 acquainted with parasites in the skeletal system, in the circulatory system, in the 

 brain, in the muscles, in the excretory and genital organs, and even in the organs of 

 sense. 



It is possible, and perhaps might be advantageous, to arrange and describe the 

 parasites of man according to the situations in which they are found (parasites of the 

 skin, intestinal parasites, etc.). Their description in the various stages of develop- 

 ment would, however, be disturbed when, as is generally the case, the different stages 

 are passed in different organs, and a work which treats more fully of the natural 

 history of the parasites than of the local disorders to which they give rise would 

 suffer thereby. It is, therefore, preferable to describe the parasites of man in their 

 systematic order, and to mention their different situations in man in describing each 

 species. 



A. PROTOZOA, 



BY 



H. B. FANTHAM, M.A., D.Sc. 



All those animal organisms which throughout their entire life never rise above 

 the unicellular stage, or merely form simple, loose colonies of similar unicellular 

 animals, are grouped under the term Protozoa (Goldfuss, 1820), as the simplest types 

 of animal life. All the vital functions of these, the lowest forms of animals, are 

 carried out by their body substance, the protoplasm (sarcode). Often particular 

 parts possess special functions, but the limits of a cell are never over-stepped 

 thereby. These special parts of the cell are called " cell-organs " ; recently they 

 have been termed " organellae." 



The living protoplasm has the appearance of a finely granular, viscid substance 

 which, as a -rule, when not surrounded by dense investing membranes or skeletons, 

 exhibits a distinct kind of movement, which has been termed amoeboid. According 

 to the species, processes of different forms and varying numbers called pseudopodia 

 are protruded and withdrawn, and with their assistance these tiny organisms glide 

 along it might almost be said flow along over the surface. In most Protozoa two 

 layers of cytoplasm may be recognised, and distinguished by their appearance and 

 structure, namely, the superficially situated, viscid, and quite hyaline ectosarc or 

 ectoplasm, and the more fluid and always granular endosarc or endoplasm, which 

 is entirely enveloped by the ectoplasm. The two layers have different functions ; the 

 movements originate from the ectoplasm, which also undoubtedly fulfils the functions 

 of breathing, introduction of food and excretion. The endoplasm, which in some forms 

 (Radiolaria) is separated from the ectoplasm by a membrane, undertakes the digestion 



