800 PARASITIC DISEASES. 



in size from a pin-head to a hemp-seed, or even larger, and 

 resembling small vesicles or blisters. Some are filled with a 

 clear fluid ; others contain a soft material, consisting of granular 

 matter; whilst others are hard and gritty, — and all contain 

 minute worms coiled upon themselves. 



The varying degrees of hardness and consistence of the nodules 

 mark their age ; the vesicle seems to be their earliest develop- 

 ment ; the soft, solid condition a more mature condition ; and 

 the gritty state shows that the wall has undergone calcification, 

 and that the worm has been lodged in the lung tissue for a 

 considerable period. 



The presence of these parasites in the lung does not always 

 cause irritation or inconvenience to the host. The lungs of 

 sheep killed in the primest condition are found loaded with 

 them. Occasionally, however, they induce debility, anaemia, and 

 cause death, more particularly in lambing ewes, at or about the 

 period of parturition. Many ewes died from this cause during 

 the lambing season 1874. 



In lambs, however, the parasites find their way through the 

 softer lung structure into the bronchial tubes, and there give 

 rise to irritation, and to the symptoms of the " lamb disease." 



It is supposed that the parasite is developed in the lamb only, 

 and that those found encysted in the lungs of sheep have been 

 long imprisoned as it were by a boundary line of plastic inflam- 

 mation, which finally becomes calcified, and offers an impassable 

 barrier to the movement of the strongyle. 



Whilst admitting the greater frequency of the affection in 

 lambs than in sheep of a more mature age, I cannot subscribe 

 to the above conclusion, as the results of examinations of the 

 lungs of four or even five year old ewes have shown con- 

 clusively that many cysts are not in a state of calcification — a 

 condition that they certainly would be in, if the parasitic invasion 

 had occurred when they were lambs. The manner by which 

 parasites gain access to the lungs lias been a matter of contro- 

 versy. Dr. Edward Crisp, in an essay on this disease, for which 

 a prize of £30 was awarded by the Bath and West of England 

 Agricultural Society, accounts for their presence in the lungs by 

 direct passage into the trachea from the mouth, where they have 

 been forced from the stomach during the act of rumination. Mr. 

 Dickinson, M.E.C.V.S., Boston, Lincolnshire, Professor A-rmatage, 



