The Sclerostome Worms of the Horse. 



■uticle is well ringed, thirdly there are no traces of lateral 

 i^pines, fourthly they are smaller in size, the males varying from 

 8 — 12 mm., the females lO to 15 mm., lastly they are not 

 nearly so often found in copula as the white species. For this 

 worm I propose tcmpoi'arily the name of ruhrum. 



Sir George Brown informs me that for the last 30 years 

 veterinary surgeons have taken this red species to be 

 tetracanthum. Discrepancies in regards to the identity 

 and characters of tetracanthum have been pointed out also 

 by L. Savoiirnin. 



The life-histories of the above are briefly as follows (as 

 far as we at present know) : — Equintnn — in this species we 

 have a tolerably complete history. The ova laid by the 

 female come out in the horses' dung and hatch, I find, in from 

 5 to 8 days on damp sand into little white cylindrical embryos. 

 These embryos shrink up in their old skin, which forms a kind 

 of puparium in which the larval worm moults twice. The 

 horse obtains these embryos in this condition in water and 

 doubtless with grass. These embryos then burst out of the 

 shell and enter the mucous membrane of the caecum and 

 colon ; here some remain, forming small tumourous lumps, but 

 the majority get taken along with the blood and eventually 

 reach the posterior branches of the dorsal aorta, where they 

 form aneurisms. The mesenteric artery is particularly liable 

 to their invasion. In these aneurisms the asexual worms 

 form a thrombus in which they partly live. After a sojourn 

 of some months in this position they leave their abode and 

 are carried on by the blood back to the walls of the caecum 

 and colon, here they bury themselves in the sub-mucous 

 coat and form tumourous cysts along with those that remained 

 there at first. Eventually the worms in these cysts mature 

 cind escape into the intestinal contents, become sexual, and 

 grow into the large S. equinum. They are sometimes so 

 abundant that they completely block up the artery and cause 

 it to rupture. The result of their presence is internal 

 haemorrhage and violent colics, which, in a particular case 

 notified to me, was undoubtedly the cause of death. The 

 filly in question had been dosed with thymol, but only in 

 five-grain doses ; it does not appear that this substance has 



