TirinsmisHt'on 



36 



No statistics of the occuruence o£ bilharzia in this village were 

 obtainable. A rapid examination of the urine of fifty-four boys in 

 two of the village schools showed bilharzia eggs in forty-nine cases. 

 The determinations were completed within an hour, and the positive 

 results based upon single drops of freshly passed urine taken without 

 either sedimentation or preliminary use of the centrifuge. Most of 

 the boys were under 12 years of age, and had been born and reared 



Fig. 12.- Marg Canal almost dry during a summer rotation. 



in the village. It seemed reasonable to suppose that the bilharzia 

 infection was derived from the Marg Canal, with its terminal 

 branches and subsidiary agricultural drains around the village. It 

 was decided, therefore, to make a complete census of all fresh- 

 water molluscs in this the sole possible source of infection. 



The Mollusca of Marg. 

 A fortunate circumstance enabled us to make practically certain 

 that no species living on or in the muddy bottom of the canal was 

 overlooked. During the summer mouths the water coming from 



