THE INFLUENCE OF PARASITES 9 



affect its host by depriving it of this material. The case is different 

 when the parasites are very numerous, especially when the heavily 

 infested host happens to be a young individual needing all it ingests 

 for its own requirements, and therefore unable to sustain the drain of 

 numerous intruders in the intestine. Disturbances also set in more 

 rapidly when the intestinal helminthes are blood-suckers, the injury 

 to the host resulting from the kind of food taken by the parasite. 



Generally, the disorders caused by loss of chyle are insignificant 

 when compared with those induced by the GROWTH and agglomera- 

 tion of the helminthes. The latter may cause chiefly obstructions of 

 small vessels or symptoms of pressure in affected or contiguous organs, 

 with all those complications which may arise secondarily, or they may 

 even lead to the complete obliteration of the organ invaded. Of course 

 the symptoms will vary according to the nature of the organ attacked. 



In consequence also of the MOVEMENTS of the parasites, disorders 

 are set up that may tend to serious pathological changes of the 

 affected organs. The collective migrations, undertaken chiefly by 

 the embryos of certain parasites (as in trichinosis, acute cestode 

 tuberculosis), are still more harmful, as are also the unusual migrations 

 of other parasites, which, incidentally, may lead to the formation 

 of so-called worm abscesses or to abnormal communications (fistulae) 

 between organs that are contiguous but possess no direct connection. 



Recently, several authors have called attention to the fact that 

 the helminthes produce substances that are TOXIC to their host ; and 

 the effects of such poisons explain the pathology of helminthiasis 

 far more satisfactorily than the theory of reflex action. 



In a number of cases these toxic materials (leucomaines) have been 

 isolated and their effects on living organisms demonstrated by actual 

 experiments. It also appears that the absorption of materials formed 

 by the decomposition of dead helminthes may likewise cause toxic 

 effects. However, our knowledge of these conditions is as yet in 

 its initial stage. 1 



Nearly all the symptoms caused directly or indirectly by parasites 

 are of such a nature that the presence of the parasites cannot be 

 diagnosed with any certainty, or only very rarely. The most that 

 can be done is to deduce the presence of parasites by the exclusion 

 of other causes. Fortunately, ho\vever, there are sufficient means 



1 Moursson et Schlagdenhauffen, " Nouv. rech. clin. et phys. sur quelq. liquides organ.," 

 C. R. Acad. Set,, Paris, 1882, p. 791 ; Debove, " Del'intox. hydat.," .#**//. et Mint. Soc. med. des 

 Hopit., 1888 ; Linstow, v., " Ueb. d. Giftgehalt d. helm.," Internat. Monatsschr. f. Anat. u. 

 Phys., xiii, 1896; Peiper, "Z. Symptomatol. der thier. Paras.," Deutsche med. Wochenschr., 

 1897, No. 40; Mingazzini, P., " Ric. sul veleno d. elm. int.," Rass. intern, d. med. 

 modern. Ann., 1901, ii, No. 6; Vaullegeard, A., " Etud. exp. et crit. sur 1'action d. helm.," 

 Bull. Soc. Linn, de Normandie, 1901, 5, Ser. T, vii, p. 84, and others. 



