122 THE EFFECTS OF PARASITES ON THEIR HOSTS. 



The belief in the absolute injuriousness of parasites, already shaken 

 by these considerations and doubts, received a still ruder shock, as 

 their wide distribution and frequent occurrence in certain animals 

 became known. Men began not only to deny the existence of speci- 

 fic worm-diseases, but to think themselves justified in maintaining 

 that it was exceptional for the parasitism to cause any disturbance of 

 health. It is true, however, that such opinions were held for the 

 most part by naturalists and helminthologists. The physicians for 

 the most part still held to the old opinions. Wherever there was 

 any doubt as to the nature and origin of a disease, worms were blamed ; 

 and " worm-irritation," " worm-fever," and other worm-diseases were 

 very common terms both in theory and practice. And if by chance, or 

 in consequence of medical treatment, a worm left the patient, they con- 

 sidered the diagnosis verified, and the cause of the disease established 

 beyond a doubt. 



The professional helminthologists, headed by Eudolphi and 

 Bremser, although, as we have said, decidedly opposing these views, 

 could not deny that certain pathological conditions, especially those of 

 the digestive apparatus, were generally, connected with the presence of 

 worms. . They were, however, disinclined to believe that tliese condi- 

 tions were directly due to worms, but sought, in accordance with their 

 theory of the spontaneous generation of Helminths, to show that there 

 were certain conditions productive of worms. They spoke of a " pre- 

 disposition to worm production " referable to definite pathological pro- 

 cesses, of a " Diathesis verminosa," which they sometimes even called 

 " verminatio," a worm disease without worms ! Thus Bremser,^ the 

 famous Viennese helminthologist, says, " By a worm disease I mean 

 any disturbance or interruption in the functions of the primary or 

 se'condary digestive and nutritive organs, whereby substances are 

 formed and collected in the alimentary canal, which under favourable 

 circumstances may, but do not necessarily, produce worms : I mean, 

 in short, the material factors of worm production. So that worms in 

 the alimentary canal are not an original disease, and indeed can only 

 rarely be regarded as a disease at all, but are much more frequently 

 the sign of the diseased state of the organs in question, or of some in- 

 terruption in the co-operation of these organs, from which state many 

 results may arise without the presence of worms." 



After what has been already said concerning the life-history and 

 origin of the Entozoa, it is unnecessary to criticise these opinions 

 minutely. "We may now regard it as completely established, that 

 parasites do not originate from a diseased condition, but from germs 

 intruding or introduced, and they especially originate where these 



' " Lebende WunnBi' ira lebenden Kbrper," p. 119. 



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