Parasites of the Circulatory System. 409 



the presence of the parasite, and I^aulanie in 1884 fully confirmed 

 Rivolta's conclusion. The term bursatti is freely applied in 

 America to sores which appear in horses in summer only, and 

 heal up during cold weather, but inasmuch as the worms have 

 not been demonstrated in the American lesions, and the "in- 

 supportable pruritus " is habitually absent, one must hesitate to 

 identify the two affections. (See Bursatti, Leeches p. 43). 



Filaria Irritans. As we are only acquainted with the larvae 

 as met in horse's skin, the true place of this parasite, in helmin- 

 th ology, is somewhat uncertain. 



" It is a very fine worm which may attain a length of 3 mm. 

 and the head of which is sometimes a little distinct from the body : 

 the tail is attenuated, terminated in a point and margined by fine 

 notches. The mouth is orbicular and appears to be provided with 

 lips. A short distance from the head is seen an opening. The 

 anus is placed at the point where the body is attenuated to form 

 the tail. The skin is delicately striated transversely." Ercolaui 

 found the tapering tail habitually bent under the body and making 

 frequent movements of abduction. 



Rivolta believes that the larvae present in the manure or damp 

 earth bore their way into the skin, and Megnin suggests that they 

 are simply the young of the Oxyuris curvula, but there is no suf- 

 ficient evidence in support of either position. The oxyuris is so 

 common in the intestines, that the summer sore should have been 

 far more prevalent, if Megnin's contention were correct. With 

 greater plausibility Laulanie claims that the ovum or embryo 

 enters the digestive tract from which the young worm bores its 

 way into the skin. Where or in what form it reaches maturity 

 and reproduces its kind is as yet unknown. 



The presence of the worm in the centre of the caseous debris of 

 the lesion implies that it is the essential factor of causation. It is 

 not, however, easy to explain the fact that but one horse in a 

 stable suffers for year after year from the local lesions when once 

 started, without any tendency to implicate other horses standing 

 along side or working with him in the team. It would seem as 

 if the disease should be cut short by the death or elimination of 

 the larval worms, and that the other horses in the same stable 

 subjected to precisely the same environment should also contract 

 the affection. 



