236 



INTESTINAL PARASITES. 



by placing a drop of faeces on a slide and placing a cover-slip 

 over same and examining with an ordinary eye-piece and 16 

 m.m. objective, measures 60-70 by 35-50 //.. They are 

 oval in shape and have a very thick albuminous envelope, 

 which has a rough fringed appearance. Usually, on account 

 of pigment absorbed in the intestines, the ova, especially the 

 envelopes, are colored from yellow to reddish brown. Infec- 

 tion may take place through infected food or by means of dirty 

 hands. Sometimes children constantly reinfect themselves by 



scratching about the anus, 

 FIG. 82. and thus infecting their 



hands, etc. This worm may 

 be present in any part of the 

 alimentary tract. 



OXYURIS. 



Next in frequency among 

 the intestinal parasites is the 

 se(d y thread, or pin worm, the 



Oxyuris vermicularis (von Jaksch): a, Head ; Embryo of the common pin worm 

 b, male; c, female; d, eggs. (Oxyuris vermicularis) of man, in the 



eggshell, as found in fresh faeces 

 (Leuckart). 



Oxyuris vermicularis (Figs. 82 and 83). This worm usually 

 inhabits the rectum and lower parts of the colon. The male 

 measures from 3-5 m.m. in length, .16-.6 m.m. in breadth; 

 the female is about three times as long. The ova are not seen 

 free in the faeces unless decomposition of the worm has taken 

 place. By crushing a mature female beneath a cover-glass, a 

 large number of ova may be demonstrated. They are pale 



and oval, measuring from 40-50 /. 



long. 



The endoplasm is 



