ASCARIS LUMBRICOIDES 



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The small intestine is the normal habitat of A scans lumbricoides ; the 

 worms, however, often leave this part of the intestine and wander into the 

 stomach, whence they are frequently evacuated by vomiting, or they may 

 creep through the oesophagus into the pharynx and crawl out through the 

 nose or mouth ; very rarely they may find their way into the Eustachian tube 

 or into the naso-lachrymal duct, or into the excretory ducts of the liver and 

 pancreas ; exceptionally they may gain the trachea, and they have also been 

 found in the abdominal cavity. They may bore through adhesions between 

 the intestinal wall and the epigastrium (worm abscess) ; they occasionally 

 penetrate the urinary apparatus and are passed with the urine ; in feverish 

 diseases Ascaris lumbricoides usually leaves the intestine spontaneously. It 

 is obvious that these wanderings may be accompanied by the most serious 

 symptoms ; but in sensitive persons the invasion of even only a few 

 intestinal ascarides gives rise to a series of almost inexplicable symptoms 

 (hysterical, epileptiform attacks, cerebral congestion, aphonia, &c.), which 

 cease with the expulsion of the' worms, so that many authors are driven 

 to the conclusion that the ascarides secrete a toxin. Fortunately, the 

 presence of Ascaris lumbricoides in the intestine is easily demonstrated by 

 the microscopical examination of the faeces. 



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Development. Sever il authors (Gros, Schubart, Richter, Leuc- 

 kart and Davaine) have demonstrated that the ova of ascaris 

 develop in water or moist earth after a long period of incubation. 

 Freezing and desiccation (if for not too long) do not injure their 

 powers of development ; the duration of the development depends 

 on the degree of the surrounding temperature. At a medium 

 temperature, after the varying period of incubation, it takes from 

 thirty to forty days for the embryo to become formed. The 

 spirally rolled up embryo, with its so-called " tooth," formed by 

 three papillae close together, never leaves the egg - shell in the 

 open, even if the eggs are kept for years under favourable 

 conditions. Davaine proved that the larvae hatch out in the 

 intestine of the rat but are again expelled with the faeces ; he 

 therefore concluded that the hatching likewise takes place 

 within the intestine of man, but is followed by the settlement 

 of the larvae. In the meantime Leuckart had sought to in- 

 fect himself by swallowing embryo-containing eggs, but without 

 results, he therefore conjectured that there must be an inter- 

 mediary host, and v. Linstow thought he had found it in myria- 

 pods (Julus guttulatus). Subsequently, Davaine's opinion proved 

 correct ; first of all Grassi succeeded in infecting himself by 

 swallowing 100 embryo-containing eggs of Ascaris lumbricoides ; 

 _five_ weeks after ingestion the worms had attained maturity and 

 their ovaT appeared in the faeces. Calandruccio also sought to infect 

 himself, but failed, yet he~ succeeded in infecting a little boy seven 



