Parasites. 283 



in a torpid state, floating about in the open waters, or 

 lying in moist places, for some length of time. And ' it is 

 highly probable that the embryos are dire6lly trans- 

 ferred to the alimentary canal of man from river and 

 pond water.' From experiments upon other animals 

 such as rats, it has been found that the gastric juice has 

 been sufficient to a6l upon the shells and liberate the 

 contents of the ova. Thus it appears that the round- 

 worm, unlike many other entozoa, does not need in any 

 stage of its existence to pass through the body of an 

 intermediary animal bearer, to complete its life-history. 

 And this I think is one very important reason why the 

 round-worm is so very much more common a human 

 parasite than many other entozoa ; and also why it is so 

 very much more common in countries like British Guiana, 

 because there are so very many more facilities and 

 opportunities for drinking foul water, such as our 

 trench-water. And without doubt these entozoa are met 

 with chiefly amongst the lower classes of our population, 

 such as would not hesitate to imbibe freely of water 

 however foul. 



The Anchylostomum duodenale or Dochmius duodenale 

 is likewise of only too frequent occurrence amongst 

 inhabitants of British Guiana. It is of much smaller size 

 than the round-worm, being only about one-third of an 

 inch in length, and on that account is much more liable 

 to be overlooked in post-mortem examinations. The 

 worm was first discovered by Dubini at Milan. It is 

 extremely common in Egypt where the disease it gives 

 rise to is called " Egyptian Chlorosis." And without 

 doubt it is to be found in all tropical countries. And 

 these parasites were the sole cause of the great havoc 



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