i6 
THOMPSON YATES LABORATORIES REPORT 
The free embryos measure 220-230 /u. long by 9-1 1 /j. wide. 
The life history is unknown. The male and female live together in the 
connective tissues of the horse and donkey giving rise to hemispherical pro- 
tuberances about the size of a nut, beneath the skin. These quickly burst and 
allow blood to escape, after which they subside and appear again in twenty-four to 
forty-eight hours in other places. Tracts of the worm can be seen in many tissues post- 
mortem. It is surmised that the embryos are taken up by some insect or crustacean. 
Fiiaria immitis. Leidy 
Syn. F. cants cordis, Leidy ; F. papulosa, haematica canis domestici, Gruby 
and Delafond. 
Body white, filiform, a little tapering at each extremity especially posteriorly. 
Anterior extremity rounded. Mouth terminal, small, simple, surrounded by six 
small indistinct papillae. Anus near the end of tail. 
The male 12 to 18 cm. long, 0*7 to 0*9 mm. broad, with spirally wormed 
tail bearing two small lateral ridges supported by papillae, four of which are larger 
than the others — there are three pre- and one post-anal papillae, Man son' however 
describes the arrangement of papillae differently. Two unequal spicules. 
The female is 25-30 cm. long, 1 to 1-3 mm. broad. The tail is short, blunt 
and curved ; vulva is at a distance of about 7 mm. from the mouth. The ova 
hatch within the uterus : the free embryos measure 285 to 295 /a by 5 /n ; their anterior 
extremities are slightly tapered and end bluntly, the posterior tapers gradually to a fine 
point. The embryos occur in large numbers in the blood of the infected animal. 
Manson observed a certain degree of periodicity, the embryos being most numerous 
in the peripheral blood at night, not disappearing entirely however during the day. 
Life history. The adult parasites are found chiefly in the right ventricle of 
the heart of the dog, fox, and wolf. 
The development of the embryos has been the subject of many investigations. 
Bancroft affirmed that he found the embryos in the intestine of Tricbodectes which 
had sucked the blood of infected dogs, and supposed these insects to play the part of 
intermediary host. Sonsino confirmed this, but recognized later that Tricbodectes canis 
does not suck blood and that Haematopinus pilifer was meant. Grassi and Sonsino 
found larvae of Nematodes in the intestine and body cavity of dog fleas, and 
concluded they were dealing with the embryos of either Spiroptera sanguinolenta or of 
Fiiaria immitis. Subsequently it was found that Spiroptera do not give rise to 
haematozoal embryos, and it was inferred that dog fleas were the intermediary hosts. 
Later Grass! conclusively proved that neither Pulex serraticeps, Haematopinus, nor 
ticks {Rhipicepbalus siculus, Koch) served as the hosts for F. immitis. In the previous 
1. Manson, Medical Times and Gazette, 1877. Vol. II. page 513. etc. 
