108 A Descrij^tion of the Thread-worm, Filaria immitis. 



rupture of the heart or obstructing the pulmonary or cerebral 

 circulation. The young brood appeared innocuous. It is clear 

 that the loss of valuable sporting animals by sudden death while in 

 apparent full health, and the idea of " foul play " as the cause, 

 have led to the elucidation of this branch of canine pathology, and 

 an inquiry into the life history of the parasite. 



Turning to the human fluids, ova and minute larvae of a 

 nematoid worm were found, apparently as parasites, in the urine 

 by Drs. Salisbury and Cobbold. Filariae in the urine associated 

 with chyluria and more or less hsematuria, probably as cause from 

 mechanical blocking of the capillaries and rupture of their walls, 

 have been detected in Germany, and also in India by Dr. Lewis, 

 A.M.D. The latter observer noted them in fifteen or twenty 

 patients, in Europeans and East Indians or natives in about equal 

 proportion. Dr. Lewis also discovered filarise in the blood in four 

 individuals, twice associated also with chyluria and the presence of 

 the worms in the urine ; one case was fatal from coexistent disease, 

 but no clue as to the nature or cause of the worm infection was 

 detected post mortem. Judging from the numbers present in a 

 drop of blood, he calculated their presence throughout the circu- 

 latory system would amount in one individual host to 140,000. 

 He ascertained that the blood filariae were similar to those found 

 in the urine. Their average size was, — length yV inch, breadth 

 ^5*0^ inch, relative proportion of breadth to length 1 to 46, length 

 of tail to total length 1 to 8. The body was filiform, head 

 rounded, tail acutely pointed, texture of body translucent but 

 becoming granular, marked by delicate faint transverse striae, a 

 foreshadowing of a differentiation of the body components into 

 organs. A delicate faint membranous capsule, like the myolemma 

 of muscular fibre, surrounded the worm during life, and in which 

 the animal moved, but this feature was not constant after death. 

 Their presence did not appear hurtful to the host beyond the 

 blocking of the renal capillaries for a temporary period. 



On the afiinity of the dog filaria to congener forms, it may 

 be observed that in the general outline of the body, the round 

 oral aperture, the blind alimentary canal, and the large uterine 

 cavity, the mature female canine worm approaches the F. medi- 

 nensis, while the broods also present certain general features in 

 common. Eoughly speaking, the links between the mature worms 

 and the ascarides and oxyurides on the one hand, and between the 

 young and the trichinae on the other hand, connect these as family 

 groups in the animal world. It is, however, when we place the 

 young canine worm side by side with the human blood filaria that 

 the closest relationship is brought out. It is evident from what 

 has been adduced as to the anatomy of the free young canine that 

 its points of accord with the human filaria completely overbalance 

 the points of discord. There are shght but insignificant diver- 



