142 THE EFFECTS OF PARASITES OX THEIR HOSTS. 



membrane ; and these structural changes cannot be without correlative 

 influence on the intestines. I have further established by experiment 

 that tape- worms may under some circumstances prove fatal. I fed a dog 

 with about 150 pieces of immature Tcenia ccenurus, each piece about a 

 span long, and forming altogether a bolus about the size of a goose's 

 egg. This I thrust into the animal's pharynx, beyond the root of 

 the tongue, in the hope that these worms would at least partially 

 develop further in their new host. This did not happen, for eighteen 

 hours after the feeding the powerful dog was a carcase. On exa- 

 mination, the stomach and duodenum were found to be filled with 

 a bloody fluid. The walls were very strongly injected, covered 

 with abundant ecchymoses, and partly with a loose layer of altered 

 epithelial cells. The same phenomena, in a less conspicuous degree, 

 could be traced to about the middle of the small intestine. The 

 tape-worms were entirely digested, but traces of them were dis- 

 coverable here and there in the small intestine ; yet I do not doubt 

 that they were to blame for the death of the dog, and would hazard 

 the suggestion that this was due to the rapid and violent movements 

 of the worms in their endeavour to escape the fatal action of the 

 digestive juices. At any rate, the common supposition that tape- 

 worms are among the slowest and most indolent of organisms is 

 certainly erroneous, as any one may satisfy himself by observing them 

 in their natural environment, the warm intestine, or even in a 

 hatching apparatus. 



But the presence of a great number of intestinal worms is by no 

 means a necessary antecedent to such pathological changes. Even a 

 single tape-worm or Ascaris can determine a more or less intense in- 

 testinal irritation, provided only that it be habitually characterised by 

 a somewhat vigorous motion. I have frequently observed a reddening 

 and loosening of the mucous membrane, like that we have cited as 

 produced by Tcenia echinococcus and T. cucumerina, in cases where 

 only a single large tape-worm or thread-worm was present, and the 

 pathological condition was so strictly limited to the area occupied by 

 the parasite that there could be no doubt as to the causal relation. l 

 Since the dissection was made immediately after death, the result 

 could be no post mortem phenomenon, but could only be referred to 

 the movements of the living worm. 



A state of intense inflammation is sometimes excited by parasitic 



1 Here might be quoted the following observation of Gb'ze (see loc. cit., p. 71) : 

 "My child suddenly died on the llth February 1778, and on post mortem exam- 

 ination on the following day there was found in the intestine, not far from the stomach, 

 a large thread-worm, which had caused a red inflammatory spot at the place where it 

 had lain." 



