CHAPTER V 



CHEMISTRY OF THE ANIMAL PARASITES l 



THIS subject has received much less consideration than its 

 importance deserves, and we are quite in the dark as to how 

 much of the effects produced by animal parasites are not merely 

 mechanical, but are due to soluble poisons that they may secrete 

 or excrete. Some of the parasites probably cause harm mechan- 

 ically and in no other way, but with most of them there is more 

 or less evidence of the formation of poisonous substances. The 

 composition of the bodies of the animal parasites is an almost 

 unexplored field, but we have no reason to believe that the com- 

 position of the cells of invertebrates differs essentially from that of 

 the cells of higher organisms. Perhaps the most characteristic 

 constituent observed in many forms is chtim, which forms a 

 large part of the outer covering of the encysted forms, and prob- 

 ably of many of the worms. Glycogen is usually abundant in 

 the invertebrates, and the animal parasites form no exception, 2 

 this carbohydrate having been found in their bodies by many 

 observers. 



Eosinophllia. One of the most characteristic features of 

 the animal parasites is that they exert a positive chemotaxis, 

 particularly for eosinophile leucocytes. 3 



An increase in the number of these cells in the blood, as well 

 as a local accumulation in the tissues nearest the parasite, has 

 been observed in infection with the following parasites : 4 Unci- 

 naria duodenalis, Strongyloides intestinalis, Ascaris lumbricoides, 

 Tcenia solium, Tcenia saginata, Tcenia echinococcus, 5 Filaria 

 bancrofti, Bilharzia hcematobia, Trichinetta spiralis, and Amoeba 

 coli. G Of these, infection with Trichinella spiralis causes the 

 most pronounced eosinophilia, presumably because of the great 



1 General references to this subject will be found in v. Fiirth's " Vergleich- 

 ende chemische Physiologic der niederen Tiere," Jena, 1903 ; and Faust's 

 " Tierische Gifte," Braunschweig, 1906. 



2 See Pfluger, Pfliiger's Arch., 1903 (96), 153. 



3 Literature by Opie, Amer. Jour. Med. Sci., 1904 (127), 477; and Staubli, 

 Deut. Arch. klin. Med., 1906 (85), 286. 



4 Literature by Bruns, Liefmann and Mackel, Munch, med. Woch., 1905 

 (52), 253. 



5 See DeVe", Compt. Rend. Soc. Biol., 1905 (59), 49. 

 6 Billet, Semaine meU, 1905 (25), 261. 



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