REPORT OF THE SOCIETY 101 



3. Nerve-irritation from the presence of parasites may manifest itself 

 in various ways. The presence of the giant nematode Dioctophyme in con- 

 tact, with the diaphragm of a dog set up spasmodic vomiting. Itching of 

 the nose is a reflex nerv^ous symptom associated with the presence of certain 

 parasites of the alimentary canal of children, while in extreme cases con- 

 vulsions and epileptic strokes may be likewise produced. 



4. The production of specific poisons or toxines by parasites is one 

 of the most important ways in which they may bring about injury to their 

 host. It is now clearly established that the evil effects of hookworm in- 

 festation are attributable not to its direct attacks but to the actions of such 

 toxines. Various species of tapeworms have been shown to affect their 

 host by similar products. Thus, Schaumann and Tallquist, 1898, fed to a 

 dog fragments of the fish tapeworm, Dibothriocephalus latus, which is known 

 to cause anemia in the human host. The result of the experiment was the 

 reduction of the red blood corpuscles of the experimental animal from a 

 normal of 3,400,000 to 1,200,000 per ccm. This haemolytic action of the 

 worm was then similarly demonstrated in vitro. Many other illustrations 

 could be cited, all emphasizing the importance of this toxine-producing 

 power of internal parasites. 



5. Finally, centers of infection may be produced by the incidental 

 injuries caused by the feeding or migration of parasites. Lesions of the 

 intestinal mucosa may permit the entrance into the circulation of typhoid 

 or other germs which might have passed through the canal without ill 

 effects. Certain types of appendicitis are clearly indicated to be associated 

 with the presence of whipworms {Trichuria trichuria). Migrating trichinae 

 have been found to carry with them pathogenic organisms causing abscess 

 and septicaemia. Of special interest in these days is the fact that parasites 

 may stimulate abnormal tissue growth in their host and that there is excel- 

 lent evidence that they may occasionally induce cancer. 



Having seen that the parasitic worms must be reckoned with as im- 

 portant foes of man and his domesticated animals, we may now examine 

 more closely the groups concerned and some typical life histories. This 

 will serve to illustrate that methods of control of parasitic forms must be 

 mainly preventive, and that a knowledge of life-histories affords us the only 

 clue to vulnerable points of attack. 



The parasitic worms of man and animals belong almost exclusively 

 to the two great groups of Platyhelminthes, or flatAvorms and Nemathel- 

 minthes, or thread worms. These groups are well known to all of you and 

 we need only recall that the parasitic flatworms include the Trematoda or 

 flukes, and the Cestoda, or tapeworms. The threadworms are of two classes, 



