PARASITES OF ANIMALS. 123 



sands of eggs, in which the embryos are considerably de- 

 veloped before they are laid. The embryos enclosed within 

 the eggs are shaped somewhat like tad-poles, the slender tail 

 being bent up against the lower side of the body, which faces 

 the flattened side of the egg. The body is broad and well 

 fills the egg. The full history of the development of the eggs 

 is not yet known. It is probable, however, that a portion of 

 the eggs imbedded in the mucus membrane of the intestine 

 hatch in that situation, remaining thus in the same person. 

 But it is also probable that the eggs that are discharged will 

 hatch in water, and that persons become infested by swallow- 

 ing the embryos with their food and drink. 



Symptoms. 



The most marked symptom of these parasites is an intoler- 

 able itching in and about the anal orifice, which is generally 

 worst in the evening or during the night, when the worms are 

 migrating or changing their localities. This is usually accom- 

 panied by sensations of heat and inflammation. Not unfre- 

 quently, by irritation of the adjacent nerves, they cause 

 similar sensations in the genital and urinary organs, which 

 sometimes become very distressing. They sometimes even 

 migrate into the genital passages of female children, causing 

 great irritation and very serious symptoms. By the irritation 

 of the sexual organs, in both sexes, various unfortunate sec- 

 ondary diseases and bad habits not unfrequently result, 

 especially if they occur at the period of early puberty. Other 

 symptoms caused by the irritation of the nervous system, are 

 restlessness, general nervousness, involuntary twitchings, 

 itching of the nose, chorea, convulsions, and sometimes 

 epileptiform seizures. 



Remedies. 



The various medicines ordinarily used as anthelmintics, or 

 vermifuges, will often bring away large numbers of these 

 worms. Of these the etherial extract of male fern is probably 

 the best, but santonine and panna have been used with good 

 results. Ordinarily they can be treated more easily and 

 effectively by means of injections of cold, or nearly cold, 



