137 



BISTOMA LANCEOLATUM, Mehlis. 



Plate XVII, Figs. 11 to 15. 



.Description. — Body semi-transparent, spotted with brown by the eggs, length from 

 4 to 9""", width 2.5""", lanceolate, obtuse behind, attenuate forward, and terminated 

 by the oral sucker, which is nearly as large as the ventral. Integument smooth, 

 intestine with two branches, not further subdivided. Penis long, generally straight. 

 Genital orifices very close to one another. Eggs ovoid, length from 0.037 to 0.040™™. 

 (Neumann.) 



The life history of this parasite seems to be as yet unknown, but it is 

 believed to be analogous to that of Distoma hepaticum. The embryo 

 (Fig. 11) differs from that of D. liepaticum in being globular, armed with 

 a cephalic spur, and in being ciliated only over the anterior third of the 

 body. Its movements are said to be slower. 



Ercolaui has shown that young embryos measuring 1""^ first show 

 traces of a digestive system (Fig. 14), and that the digestive system is 

 preceded by groupings of cells, which first outline the testicles, then the 

 penis, and lastly the ovaries. Two species of suails, Planorbis margi- 

 natus and Helix carthusina, -which contained cercariae, have been pointed 

 out, the former by Willemoes-Suhm and the latter by Piana as the in- 

 termediary hosts of the fluke. 



This species of fluke never produces symptoms or lesions as grave as D. hepaticum, 

 and can only occasion aqueous cachexia or dropsy. This relative harmlessness is at- 

 tributed by Leuckart to its small size and the absence of spines ou the skin. The two 

 species are most often found together in the same host. By reason of its minute size, 

 D. lanceolatum penetrates into the finest biliary canals, where the young D. liepaticam 

 can not enter. Because the individuals of the former species escape observation on 

 account of their small size they appear to be fewer in number. Friedberge'r has ex- 

 tracted some thousands from the biliary passages by squeezing the liver. They are 

 also found in great numbers in the gall bladder and in the intestine at the time of 

 their emigration. (Neumann.) 



The means of prevention and treatment are the same for this as for 

 Distoma hepaticum. Treatment is of more avail. 



