Etioloii'y. 69 



11. Strongylus canis bronchialis Osier (Filaria tracheobron- 

 chialis). This worm, the zoological position of which has not yet been 

 definitely decided, is sometimes found in wart-like nodules of the trachea 

 or larger bronchi in dogs. 



12. Strongylus vasorum Baillet. The ova and embryos of this 

 worm are found in the lungs of dogs (found heretofore in the neigh- 

 borhood of Toulouse, France, and in Italy). 



In the respiratory passages or in the lungs of cats are found 

 exceptionally Trichosoma aerophilum C'replin, also the eni))ryos of 

 Ollulanus tricuspis Leuckart. The individual species of domestic ani- 

 mals may therefore contain several species of strongylus, viz. : 



In sheep : Str. filaria, commutatus, rufescens, capillaris. 



In hogs : Str. paradoxus. 



In cattle : Str. micrurus and pulmonalis. 



In horses and asses : Str. micrurus and Arnfieldii. 



In dogs : Str. canis bronchialis and Str. vasorum. 



In cats : Str. pusillus. 



In rabbits : Str. commutatus. 



As to the frequency in occurrence of individual si)ecies of lungworms in 

 domestic animals which harbor several species of strongylus, the following may be 

 said: In sheep one finds, most commonly, according to the general view, Strongylus 

 capillaris and exceptionally only Str. paradoxus or Str. minutissimus; not "un- 

 commonly, however, there may be more than one, and in fact all of these three 

 species of strongylus in one and the same hoi-t aniii.'al. It is said that the disease 

 generally takes an enzootic character if the Str. filaria is present, more rarely if 

 Str. capillaris, and still more rarely if other species of strongylus are present. Some 

 observations, however, point to the fact that these conditions may be changed 

 materially, particular!}' in some parts. Ranke found Str. capillaris in all sheep 

 marketed in London. Strose found this same worm in 66%, and Schlegel in 22% 

 of the sick sheep, while the last-named author found Str. commutatus in .3.3% and 

 Str. filaria in only 4%. It is also believed that goats are infecte<l most commonly 

 with Str. filaria; but Schlegel found the Str. capillaris in 92% of sick goats. 



The development of lungworms is only partially kno^^^l and in 

 some species totally unknown. The worms deposit their ova in the 

 air passages of the host, whereupon the embryos are either set free 

 immediately, or, in the oviparous species, only after some time ; and 

 they are either expelled directly M'ith the bronchial secretion into 

 the outside world or they get into the pharynx, are swallowed and 

 voided with the feces. Observations made on the embryos of Str. 

 filaria have shown that, provided the temperature and moisture are 

 favorable, the larvae which have arrived in the outside world go through 

 several castings in moist soil, in pools of water, in marshes or in wet 

 grass (casting may occur even in the air passages of the host in 

 Str. capillaris) ; and they live then, according to some authors (Leuck- 

 art, Railliet) for some time in an intermediary host (insect, mollusc, 

 angle worm). Only after such development will the paiasites be al)le to 

 invade the air passages of certain animals and there reach sexual 

 maturity. 



According to Gerlach the period of development to S'^xual maturity 

 lasts at least eight weeks; however, the observation of Schlegel, that 

 lungworm disease in goats may appear twelve to fifty-nine davs after 

 the introduction of the ])rood of Str. capillaris, permits the conclusion 

 that sexual maturity may be attained in a shorter ti'ne than eight 

 Aveeks. (Sir. micrurus, according to Tapken, needs six to seven weeks 

 for its coMiplctc development.) The location where the worms attain 

 full sexual development varies more or less for different species. Str. 



