NEMATODA 247 



identical species, still it is evident that any person discharging 

 the eggs of lumbricoids in the vicinity of open waters becomes, 

 by that fact, a source and centre of infection. To ensure an 

 endemic it is probably only further necessary that the human 

 inhabitants should employ the contaminated water for domestic 

 purposes. But time and an increase of temperature must be 

 allowed for the bringing about of those known and unknown 

 larval changes that alike form the necessary antecedents of 

 infection. In this connection I will only add, that if the 

 present position of the question be such as I have here repre- 

 sented it to be, we see that Hosier was not far wrong when he 

 suggested that " contamination of the drinking water with the 

 eggs out of privies is to be blamed " as a source of infection. 

 According to Heller, from whom I quote, Hosier actually 

 demonstrated the presence of the eggs in water thus exposed. 

 In like manner it becomes obvious that Davaine's practical 

 remark (although it was based on the assumption of a direct 

 infection by the eggs), that filtration will probably be sufficient 

 to prevent infection, loses nothing of its hygienic value. 



The foregoing observations naturally lead one to the question 

 of frequency and distribution. Davaine holds that the com- 

 parative infrequency of this parasite in Paris is due to the free 

 use of the filter. In London, though not uncommon, the worm 

 rarely occurs in great numbers in one bearer. Those cases in 

 our hospitals, where considerable numbers have been present, 

 have usually come up from suburban or country places. Heller 

 states that these worms were found in 9'1 per cent, of post 

 mortems conducted at Dresden, in 12 per cent, at Erlangen, 

 and in 17 per cent, at Kiel. He quotes Huss as stating that 

 no one is free from this worm in Finland. The prevalence of 

 large round worms in warm countries generally is well known. 

 Throughout India and the East they are extremely abundant, 

 and the same may be said of the West Indies, Brazil, and the 

 adjacent territories. Professor Dyce and others have remarked 

 on the extreme prevalence of lumbrici in the Hauritius, but 

 they are comparatively rare along the sea border. In all 

 situations where there is an abundant fresh-water supply these 

 parasites are particularly common, as in the lowlands of 

 Holland and the lake districts of Sweden. The abundance of 

 water is certainly not alone sufficient to explain the frequency 

 of the parasite, seeing that the most important factor is that 

 which rests upon the uncivilised habits of the rural population. 



