PARASITIC DISEASES OF THE LUNGS. 803 



I can offer no explanation as to the source frorii wlience tlie 

 StrongyliLs filaria is originally derived, and can only say with Dr. 

 Cobbold, that, " with the exception of the Trichina spiralis, I am 

 not aware that we have a thorough knowledge of the entire life 

 history of any of the nematode species which infest the human 

 body ; nor, indeed, can I call to mind any round-worm infesting 

 the lower animals, whose life phases, migrations, and peculiarities 

 of structure during development are satisfactorily known." 



We know, however, that the disease prevails particularly iu 

 low, damp situations ; on lands subjected to be flooded by the 

 overflowing of rivers, or after heavy rains occurring during early 

 autumn or the latter part of summer. 



Symptoms. — These are subject to some modification, depending 

 upon the seat of the parasites. In the majority of cases, they 

 are found in the lungs, in others in the lungs and digestive 

 organs, whilst in others again they are found in the stomach and 

 bowels only — the lungs being entirely free from them. Wlien 

 in the intestinal canal the symptoms are those of dysentery, 

 with foetid stools ; there is much tenesmus or straining, and 

 occasionally clots of foetid blood are discharged per rectum. The 

 lodgment of the parasites in the pulpionary tissue and bronchial 

 tubes cause, in the lamb, irritation and inflammation, indicated 

 by cough, rubbing the nose on the ground, apd accelerated re- 

 spiratory movements, whilst in the more mature animal — the 

 sheep — the presence of the parasite may induce no diagnostic 

 signs, even in those which succumb, and it is only after death 

 that the cause of the emaciation and antemia, which may have 

 been present during life, is discovered. In many cases the 

 abdominal symptoms are accompanied by depraved appetite, 

 intense thirst, and even colicky pains. 



When the parasites are in both the lungs and bowels, there 

 will be a combination of pulmonary and enteric irritation, and 

 very rapid sinking. If the expectoration and alvine discharges 

 be carefully examined some of the parasites are sometimes 

 discoverable. 



Treatment.— This naturally divides itself into preventive and 

 curative. 



To prevent the disease lambs require to be fed on fresh 

 pastures ; second and third year crops are to be specially 

 avoided, if they have been previously grazed by sheep. If the 



