226 1'IIALEN AND NICHOLS. 



found ia the liver, with slight cirrhotic changes. Manson speaks of the 

 occasional presence of small numbers of ova in the liver, but knows of no 

 pathological change caused by their presence. Other writers on the 

 subject are a unit in regarding the liver as a neglible factor in Bilhar- 

 ziosis. 



The question immediately suggests itself, why, in Bilharzia disease, 

 should the ova cause such profound changes in the intestines and bladder, 

 to the practical excluson of alterations in the liver, while, in a disease 

 as closely allied as the one under discussion in our paper, the liver should 

 be the chief site for the lodgement of the ova and its pathology the chief 

 features of the malady? 



Dr. Letulle has published an extremely interesting article = in which 

 he worked out, with the most faithful attention to details, the histologic 

 changes in a case of intestinal Bilharziosis, and from them drew some 

 convincing conclusions. It is not our purpose to discuss the process of 

 reasoning by which these conclusions were reached, and, therefore, we 

 will give only his explanation of the local distribution of the ova and the 

 resulting pathologic changes. According to his idea the pair of worms, 

 with the female occupying the gynocophoric canal of the male, habitually 

 inhabit the larger venous radicles of the portal system. When the time 

 comes for the deposition of the ova, the worms, still together, migrate 

 to the smaller veins until, having reached such a vessel of a caliber of 

 about 1,000 fi, the male can go no further because of his size. The female 

 then leaves the male and migrates- as nearly as possible to the lumen of 

 the intestine or bladder, that is, into the venules of the submucosa where 

 the vessels are narrowed to 80 to 120 /*, and where she can go no farther. 

 She takes position in one of these small veins, completely blocking it, and 

 produces a stasis in the vessels ahead. She attaches herself by her 

 suckers to the intima of the vessel and evacuates her ova into the distal 

 portion of the vein. The pressure of the mass of ova, as well as that of 

 the blood, enable their spines to pierce the walls of the vessels, and the 

 whole mass is forced into the perivascular tissue so quickty, according 

 to Letulle, that although he saw many masses just without the vessel, he 

 did not find a single ovum within the lumen. The female having de- 

 posited her ova and waited a sufficient length of time for their migra- 

 tion, joins the male in the large vessels. 



Let lis apply these facts to Schistosomum japonicum. Here we have 

 a similar pair of worms of the same relative size, although both are 

 somewhat smaller than in the Bilharzia species. Although it is not proved 

 that Schistosomum japonicum inhabits exclusively or even habitually the 

 arterial side of the pelvic blood suppty, Catto found worms in the arte- 

 rioles in this location, and we have Manson as an authority for their 



3 Arch, de Parasit. (1905) 9, 329. 



