202 INTRODUCTION TO THE WORMS 



likely to incriminate them in nearly every morbid condition for 

 which we cannot, with equal readiness, discover another cause. 

 It cannot be doubted, however, that many of the morbid con- 

 ditions really are, in part at least, produced by intestinal worms. 

 Much of the difference of opinion regarding the effects of these 

 parasites is no doubt due to the variable susceptibility of dif- 

 ferent individuals. 



The amount of nutriment which is absorbed by worms such 

 as A scaris and the pin worm, which live on semi-digested food in 

 the lumen of the intestine, is probably in most cases relatively 

 slight: Leuckart states that Tcenia saginata, for instance, gives 

 off about 11 proglottids a day, which would amount to one and 

 two-thirds pounds in a year. This would not, of course, repre- 

 sent more than a fraction of the food materials used. Such a 

 loss would, however, be inappreciable in adults, though it would 

 be felt in growing children unless compensated for by increased 

 appetite. Many intestinal parasites, as the hookworms, devour 

 cells of the mucous membrane and suck blood, sometimes causing 

 extensive bleeding. 



The most serious injury from intestinal worms is undoubtedly 

 the toxic effects of their secretions and excretions. We know 

 that the diseases caused by most Bacteria and Protozoa are 

 the result, not of the actual damage done by the parasites in 

 devouring tissues, but of the poisonous waste products and se- 

 cretions given off by these organisms. Until recently little was 

 known about the toxic effects of worms, but that toxins were pro- 

 duced by them was evident from symptoms disproportionate to 

 the mechanical injury the parasites could do, and from effects 

 which could in no way be the direct result of mechanical injury. 

 In 1901 a French worker, Vaullegeard, actually obtained from 

 certain tapeworms and from A scan's toxic substances which 

 acted upon the nervous system and upon the muscles. Recent 

 investigations by Flury have shown that A scaris, a nematode, 

 contains certain substances which are very irritating to mucous 

 membranes, other substances which have blood-destroying and 

 tissue-destroying properties, and still others which have an in- 

 toxicating effect on the nervous system, causing hallucinations, 

 delirium and other disturbances. These toxins, derived from 

 the body and excretions of Ascaris, when introduced into a ver- 

 tebrate animal, cause the same symptoms which often accom- 



