THE ANIMAL PARASITES OF MAN 



By E. PEIPER, Greifswald 



By " animal parasites of man " we mean the organisms which live tempo- 

 rarily or permanently on or in the body of man and derive their nourishment 

 from it. There is no difference, properly, between animals that live as para- 

 sites and those that live free. For, on the one hand, there are parasites — e. g., 

 the ascaris nigrovenosa (this species, indeed, does not live on man) — which 

 produce mature offspring capable of living free, and, on the other hand, ani- 

 mals which usually live free may appear as parasites. Thus, the larvje of 

 flies, which usually live on decaying organic substances, are found " occasion- 

 ally" as parasites in man, either in the intestinal canal or in suppurating 

 wounds. These occasional parasites must not be classed with the so-called 

 " pseudoparasites." By the latter we generally mean foreign bodies of various 

 kinds and origin which are manifest per vias naturales. 



As stated, we distinguish between a temporary and a permanent parasitism. 

 Fleas and bed-bugs infest man only transiently. The development of these 

 organisms is independent of the human body. Temporary parasites include 

 the ectoparasites (or epizoa) which inhabit the skin, the conjunctival sac, the 

 mouth, the nose and its accessory cavities. It is true, the ectoparasites also 

 include some permanent parasites. Most of the permanent or stationary para- 

 sites are found as entoparasites or entozoa in the internal organs : in the intes- 

 tinal canal and the glands belonging to it, in the lungs, in the heart, in the 

 brain, and in the muscles. But the permanent parasites are not all entopara- 

 sites, for many of them live also on the skin. Lice and sarcoptes hominis 

 rarely leave the body of man upon which they develop from the ova and 

 multiply. 



Many parasites, such as tenia, ascarides, and ankylostoma inhabit man 

 only when mature; others,- such as the echinococcus, only during a certain 

 period of its development. Man, therefore, is either the actual host or only 

 the intermediate host. For many parasites, such as tenia solium and tenia 

 saginata, man has the doubtful honor of being the only host. But, man also 

 becomes the host of parasites which, as a rule, select another host animal. 

 Thus, the cysticercus cellulose occur not only in the pig, deer, and cat, but 

 by autoinfection also in man. Balantidium coli and echinorhyncus gigas are 

 specific parasites of the pig, but occasionally they are found in man. 



Since remote times physicians and zoologists have attempted to ascertain 

 the origin of the parasites. As a rule, this has been easy with the ectopara- 

 sites; but exceedingly difficidt with the entoparasites. For not only in the 



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