44 The Philippine Journal of Science 1923 



In experimental animals, hatching occurs in the small intes- 

 tine, as will be shown presently, and the empty eggshells are 

 nearly always without the operculum. The larvae appear 

 coarsely granular, and the granules obscure the internal organs. 



FEEDING EXPERIMENTS 



Many attempts were made to bring about artificial infection 

 of guinea pigs with Oxyuris equi with a view of determining 

 the behavior of the larva? in these animals, with special refer- 

 ence to their possible migration through various organs com- 

 parable to the migrations of Ascaris larvae. Oxyuris equi eggs 

 cannot be sucked up in pipettes for purposes of feeding them 

 to animals, because they stick to the surface of the glass. After 

 several trials the following method was selected as being the 

 most suitable for the purpose. Beakers containing eggs on the 

 surface of liquid media were tilted, thus causing the eggs to 

 adhere to the sides of the vessel. In an hour or two, the eggs 

 were sufficiently dry and were scraped off with a knife and 

 placed in small gelatine capsules which were forced down the 

 oesophagus of the guinea pigs. 



Guinea pigs were killed within eighteen, twenty-four, and 

 forty-eight hours after feeding them eggs, as well as after 

 longer intervals, and various portions of the alimentary canal 

 were examined for the detection of larvae but none were found. 

 Numerous press preparations of the liver, lungs, and other 

 organs, as well as of the blood, also yielded negative results. 

 That the larvae hatched in these guinea pigs was evident from the 

 fact that empty eggshells which had lost their opercula were 

 found m the faeces of these animals. In the earlier feeding ex- 

 periments the eggshells were overlooked because the faecal sedi- 

 ment alone was examined. The shells are absent in the sediment 

 but float on the surface of the faecal emulsions. 



Guinea pigs killed within an hour or two after they had been 

 fed eggs of Oxyuris equi contained nonhatched eggs in the 

 stomach, and nonhatched eggs, free larvae, and empty eggshells 

 m the intestine. The embryonated eggs in the stomach ex- 

 hibited no movements. In view of the fact that larvae readily 

 emerge from the shells in vitro, their failure to hatch in the 

 stomach is probably due to a paralyzing effect of the stomach 

 environment on their movements, thus preventing their emer- 

 gence from the shell. 



Seurat(8) quotes Heller (1913) who states that the pinworm 

 of man, Enterobius {Oxyuris) vermicularis, hatches in the 



