212 ENTO-PARASITES AND HYGIENE. 



only one part of the body — the brain, the eye, the 

 stomach, etc., so that on examination of the interior of 

 an animal rather queer collections may sometimes be 

 made. Leuckart, in Leipzig, relates a case where a black 

 swan was dissected and the following specimens found 

 therein: 24 filaria in the lungs, 60 syngamus in the trachea, 

 more than 100 spiroptera in the stomach, many hundred 

 holostomum in the small intestine, about one hundred 

 distomum in the large intestine, 22 other distomum in the 

 CESophagus, and several more iu small nuuib'^rs, eight 

 different kinds at the same time — and the biiu, vvhen 

 alive, is said to have given no sign of uneasiness. 



There are different degrees of parasitism, beginning on 

 one side with such individuals as visit their hosts only 

 when they are driven by the want of food, leaving again 

 when they are satisfied and, not returning until they 

 feel hunger again; on the other side with such as are 

 permanently fixed on or in their host, the latter furnish- 

 ing not only food, but also shelter. The former class may 

 be called temporary parasites. Among them are those in- 

 sects which cling and suck the blood of man, certain flies, 

 the leech, etc. ; the others are the stationary or permanent 

 parasites, which are characterized by the fact that they 

 live always on or oftener in their hosts, even in organs 

 which seem to be completely closed up, so that one often 

 does not suspect the presence of any parasite inside. 

 Another marked difference between the two classes is the 

 fact that while the former have mostly a well developed 

 locomotive apparatus and highly perfected organs of 

 sense, which indeed they need in order to move around, 

 and to find a victim for their craving for food, the ento- 

 parasites, those which live in the interior of other ani- 

 mals, have more or less lost the segmentation of their 

 bodies, and with it the power of locomotion as well as 

 the ability to receive through their senses impressions 

 from without. They have become so helpless that they 



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