WORMS. 



211 



ton and jfirst named by Richard Owen, who published a very inaccurate description 

 of them in 1835, but the origin and dangerousness of these parasites was never sus- 

 pected until 1860, when the investigations of Zenker, Leuckart, Pagenstecher, and 

 Virchow suddenly revealed the dan- 

 ger by ascertaining the history of the 

 trichina and its pathological action. 

 The whole civilized world was horri- 

 fied at the discovery of the great and 

 unthought-of risk which our daily 

 meals involve. Everywhere the in- 

 formation was spread, and never, per- 

 haps, has any subject occasioned such 

 universal discussion as this new know- 

 ledge. In the intestine the trichina 

 grows rapidly, the female becomes 

 a"bout an eighth of an inch long, but 

 the male does not measure over a six- 

 teenth. The eggs in the feniale have 

 no shell, and develop to tiny embryos 

 within the body of the parent. The 

 adult worm is thin and tapering to- 

 wards the head. A number of related 

 species and genera are known, but 

 none are so dangerous as the 7Vi- 

 china spiralis, although one form, the 

 Trichocephalus dispar is not rare in 

 the human colon. 



Of the Strongtlid^ several 

 species attack man, for example 

 Eustrongylus gigas, Dochmius duo- 

 denalis, etc., but the species we select 

 for a special biography is the one so 

 detested by poultry raisers as the 

 cause of the " gapes." The parasite in 

 question goes by the name of Syn- 

 garmis trachealis, and inhabits the res- 

 piratory passages, tracheiB and bronchi 

 of birds, living in bunches, which soon 

 enlarge so much that breathing be- 

 comes difficult to the unlucky bird, 

 which gasps for air, — the name 

 "gapes" refers to the characteristic 

 symptom of the disease. The generic 

 name Syngamus refei-s to the pecu- 

 liarity of the small males of attaching themselves to the large females to form indis- 

 soluble pairs. The constant effort to dislodge the parasites by coughing serves to 

 expel the eggs laid by the female ; the eggs are thus scattered about, and are swal- 

 lowed again by other birds, and thus the disease is spread. In a hennery the malady 



Vm.lSS.—Syngamus iractiealis ; a, male; 6, female. 



