CHAPTER V 

 CHEMISTRY OF THE ANIMAL PARASITES ' 



This subject has received muck less consideration than its import- 

 ance 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 probabl.y cause harm mechanically and in no other way, 

 but with most of them there is more or less evidence of the forma- 

 tion 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 composition 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 chit in, which 

 forms a large part of the outer covering of the encysted forms, and 

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

 the invertebrates, and the animal parasites form no exception,- this 

 carbohydrate having been found in their bodies by many observers. 



Eosinophilia. — One of the most characteristic features of the 

 animal parasites is that they exert a positive chemotaxis, particularly 

 for eosinophile leucocytes.^ 



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 practically all the animal parasites.* Of 

 these, infection with Trichinella spiralis causes the most pronounced 

 eosinophilia, presumably because of the great number of parasites 

 present in the tissues at once. That the eosinophilia is due to the ac- 

 tion of the soluble products or constituents of the parasites has been 

 shown by experimental injection into animals of extracts from the 

 bodies of the parasites. Calamida lias found that extracts of dog 

 tapeworms also, when placed in the tissues in a capillary tube, cause 

 an accumulation of eosinophile cells in the tube.^' Experimental in- 

 fection with excessive numbers of trichinella causes a rapid diminu- 



1 General references to this subject will be found in v. Fiirtli's "Verirli'ichende 

 chemische Physiolofjie dor niederen Tiere." .Tena, 190.3; Faust's "Tierische Gifte."' 

 Braunscliweip, 100(»; Kocb. Er<;ebnisse Pathol.. 1010 (xiv (1) ), 41. 



2 See Pniifrer, Pniiper's Arch.. 190:? (OH), l.l.'^ 



3 Mtorature bv Oi)ie. Amer. .Tour. Med. Sci., 1904 (127). 477: Rtiiubli. Deut. 

 Arch. klin. Med." 1906 (S.5), 280; Hubner, ihid., 1911 (104), 2HG; Schwarz. Frgeb. 

 allfr. Pathol.. 1914 (17,). 1.38. 



4 Litcratino by Pruns. Liefmann and Miickel, Miinch. nied. Wocli.. 190,") (ri2), 

 253: Vallillo, Arch. wiss. u. prakt. Tierhk., 1908 (34), 50.'). 



Nefrative results were obtained with extracts of flclrrostoiiia cipniiiiu) by 

 Grosso (Folia llcniatol., 1912 (14), 18). 



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