JOINAL OF AGRldlllAlRESEARCH 



Vol. XXII Washington, D. C, Nove;mber 19, 1921 ^\^^'y^^O- 8 

 HEMOTOXINS FROM PARASITIC WORMS 



By Benjamin Schwartz ' 



Zoological Division, Bureau of Animal Industry, United States Department of 



Agriculture 



I. INTRODUCTION 



Aside from the purely mechanical injuries which parasitic worms may 

 inflict upon their host as a consequence of their migrations, displacement 

 of a certain amount of the host's tissue, bites and laceration of the mucosa, 

 obstruction of ducts, and various other mechanical disturbances, it has 

 been generally assumed that they may also produce harmful effects as a 

 result of their toxic secretions. Despite the fact that the data on which 

 the view that parasites secrete toxic substances is based, so far as they 

 have been recorded heretofore in the literature, are somewhat contra- 

 dictory, they have been accepted by a large number of investigators 

 as affording a more plausible explanation of the cliemical pathology of 

 helminthiasis than the data with reference to any other theory that has 

 thus far been advanced. With reference to the subject of toxic products 

 of parasitic worms. Wells {igiSy states: 



The subject has received much less consideration than its importance deserves, as 

 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 secrete or excrete. 

 Some of the parasites probably cause harm mechanically and in no other way, but 

 with most of them there is more or less evidence of the formation of poisonous 

 substances. 



While it must be admitted that the evidence in favor of the view that 

 parasites secrete products toxic to the host is as yet rather incomplete, the 

 fact of the existence of such toxic products can not be denied. So 

 far as they have been investigated, the serological reactions of hosts har- 

 boring parasites afford proof that parasitic worms liberate products 

 against which the host develops defense or "immunity" reactions. It 

 has been known for a relatively long time that in cases of infestation 

 with species of Trichinella, Schistosoma, Necator, and Anyclostoma a 



' Resigned December is, 1920. 



2 Dates in parenthesis refer to " Literature cited," p. 428-432. 



Journal of Agricultural Research, Vol. XXII , No. 8 



Washington, D. C. Nov. 19,1921 



aan Key No. A-62 



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