Februaey 8, 1907] 



SCIENCE 



'111 



malady are also noted. Such variations 

 have been recorded in infections with tape- 

 worms, with hook worms, with trichinog and 

 with various filarise. To what extent pre- 

 disposition and immunity influence the 

 phenomenon can not be judged at the pres- 

 ent time, owing to insufficient data and in- 

 complete observations. 



Equally characteristic with these fluctua- 

 tions one must regard also the excessive 

 degree of eosinophilia in parasitic diseases. 

 While under other conditions an eosino- 

 philia of 7 per cent, to 10 per cent, is usual, 

 with rare instances of 35 per cent, to 50 

 per cent., in infections with animal para- 

 sites 10 per cent, to 30 per cent, is the 

 average and 70 per cent to 80 per cent., or 

 even 87 per cent., the extreme. The num- 

 ber of cases with such high percentages is 

 large, even though the records in general 

 are not numerous, indicating even more 

 distinctly the usual character of the excep- 

 tional eosinophilia in such cases. 



The intimate relation of the eosinophile 

 cells to the parasite is strikingly indicated 

 by two well-established facts. The first 

 already referred to is the increase and de- 

 crease of these cells in the peripheral blood 

 as the embryos of Filaria Bancrofti appear 

 in the superficial capillaries and disap- 

 pear from them. The second was estab- 

 lished by Opie experimenting with trichina 

 on guinea-pigs. The increase in eosino- 

 phile cells does not begin until the embryos 

 start to migrate and reaches its maximum 

 when the majority of the embryos are in 

 transmission from the intestinal mucosa by 

 way of the lymphatic vessels and the blood 

 through the lungs to the muscular system. 

 Sabrazes also found a great accumulation 

 of eosinophile cells in the vicinity of hyda- 

 tid cysts. All these facts would seem to 

 indicate not only a stimulus, probably 

 chemical, inducing the multiplication of 

 the cells, but also a positive chemotaetic 

 influence which led the cells towards the 



source of the stimulus. Since the stimulus 

 originates from the parasites, the simplest 

 explanation finds it in the normal emana- 

 tions of the animal, which as waste matter 

 may be classed under the general category 

 of toxins. 



Among the physiological effects of para- 

 sitism is listed prominently the production 

 of a condition of deterioration in the blood 

 known as anemia, involving changes in the 

 red blood cells and in bone marrow. In 

 certain cases it has been possible to indi- 

 cate with some definiteness the cause, as in 

 the hook-worm anemia, already discussed. 

 External parasitism of blood-sucking spe- 

 cies, such as leeches or fish lice (argulids) 

 produces anemic conditions through direct 

 appropriation of blood, and if the parasites 

 become numerous, enough is withdrawn to 

 cause the death of the host. 



But after the elimination of these in- 

 stances there remain others in which an 

 explanation can not be given at the present 

 time. The most striking example of such 

 cases is that of the broad fish tapeworm 

 {Dibothriocephalus latus) frequently asso- 

 ciated with a severe form of pernicious 

 anemia which, indeed, is given the name of 

 a bothriocephalus anemia. Also Oxyurias 

 and Ascaris have been found less frequent- 

 ly in connection with the same pathological 

 condition, though the connection is not 

 satisfactorily demonstrated. Now in all 

 these instances the amount of departure 

 from the normal may vary from a very- 

 slight anemia to the maximum degree, 

 while in many cases there appears to be no 

 such effect from the presence of the para- 

 site. The condition is also distinguishable 

 from pernicious anemia due to inherent 

 causes in that it disappears promptly with 

 the expulsion of the parasites. Experi- 

 ments made with an extract of the Dibo- 

 thriocephalus injected into various animals 

 have been successful in some cases in pro- 

 ducing an anemia, but in other cases have 



