156 TROPICAL MEDICINE AND HYGIENE 



Instances were also given of extreme anaemia in persons 

 harbouring very few worms. 



It is now generally admitted that the common cause of 

 extreme anaemia in the Tropics is the Ankylostomnm 

 duodenale, or the closely related Necator americamis, for 

 the following reasons : 



(1) That in countries where the ankylostome is 

 common anaemia is common, and in countries and 

 places where ankylostomes are rare dangerous anaemia 

 is as rare as in England, though there are no material 

 differences in climate, amount of malaria, or in the diets 

 in the countries and places. 



(2) That in the same country the prevalence of anaemia 

 in different races varies according to the prevalence of 

 ankylostomes in these races. 



(3) That in the great majority of the cases of persons 

 suffering from anaemia there is no evidence, clinical or 

 post mortem, of any other cause for the anaemia. 



(4) The most important and conclusive evidence of the 

 relation being that of cause and effect is that treatment of all 

 other kinds fails to do more than retard the progress of the 

 disease, or to produce slight improvement, whilst expul- 

 sion of the worms is followed in a large proportion of the 

 cases by rapid and complete recovery. Administration of 

 thymol, /3-naphthol, &c., if it does not remove the worms, 

 is followed by no improvement. In the minority where 

 recovery does not occur, either death occurs too soon for 

 the amelioration to take place, or visceral lesions, particu- 

 larly fatty degeneration of the intestinal mucosa, are so 

 extensive that the removal of the primary cause could 

 not be expected to be successful in relieving the patient. 



It is admitted that numerous ankylostomes do not 

 necessarily produce profound or even slight anaemia ; but 

 in the great majority of cases where there are numerous 

 worms there is marked anaemia. 



The manner in which the anaemia is produced has also 

 been the subject of some discussion. The earlier sup- 

 position was that the Ankylostoma was a blood-sucking 



