1762 



HELMINTH INFECTIONS 



stood, but the Zoological Committee decided otherwise, and we have 

 no choice in the matter, and simply carry out the rules for the time 

 being in force. After his discovery the recognition of the disease 

 spread, at first slowly, but later rapidly. Thus Bilharz in 1853 

 and Griesinger in 1854 recognized it in Egypt,, and Wucherer in 

 1872 in Brazil, while Grassi and Parona, in 1877, drew attention to 

 the importance of finding the ova in the faeces as a method of diag- 

 nosis, and in 1899 Ashford drew attention to the importance of the 

 high eosinophilia. In 1898 Looss 1 raced the method of infection 

 by the skin, the lungs, trachea, etc., while more recently Sambon, 

 Fiilleborn, and v. Schilhng-Torgau have traced a subsidiary route 

 from the lungs via the blood-stream to the alimentary canal. In 

 1902 Stiles described Necator americanus, and in the same year 

 Boycott and Haldane found the disease in the mines of Cornwall. 

 Climatology. — ^The disease will be found wherever there is a 



suitable temperature and mois- 

 ture for the development of 

 the parasites. It is therefore 

 spread throughout the tropics 

 of America, Africa, and Asia, 

 and is also found in Queensland, 

 New Guinea, and Fiji, and also 

 in mines or tunnels in Europe, 

 where the conditions of tem- 

 perature and moisture resemble 

 the tropics. 



etiology.— The disease is 

 due to the presence of Ancy- 

 lostoma duodenale and Necator 

 americanus in the body. These 

 parasites, as far as is known, 

 live entirely in human beings, 

 and are therefore kept alive by 

 ' patients ' suffering from • the 

 disease and by ' carriers ' or 

 persons infected with so few worms that little or no symptoms 

 are produced. As already noted, the larvae live in earth, and 

 infection takes place by two routes— either through the skin or 

 by the mouth. In the latter instance, it is generally acquired by 

 eating contaminated vegetables, or through the habit of geophagy 

 met with in some natives. It is probable, in our opinion, that the 

 pathological phenomena may, partly or principally, be due to toxins, 

 either set free by the embryo in its travels from the skin to the 

 ahmentary canal, or inoculated into the blood-stream from the 

 cephahc glands of the adult worm as it grips the vilh of the intestine. 

 But absolute proof is still required of the presence of these toxins, 

 notwithstanding the work of De Giovanni, Loeb, Gabbi, Noc, Ales- 

 sandrini, and many others. Weinberg's researches on various 

 helmintotoxins must be specially mentioned. The Porto Rico 



Fig. 754. — Necator americanus, 

 (Natural size.) 



