LIFE HISTORY OF ASCARIS LUMBRICOIDES. 31 



A python that died at the National Zoological Park, Washington, 

 D. C, was infested with a species of parasite corresponding to de- 

 scriptions of Ascmis anoura. This nematode apparentl}' passes 

 through the lungs in its life cycle, inasmuch as in addition to 28 

 adult worms 115 to 160 mm. long, in the intestine of the python 

 referred to, there were found in the lungs 65 young worms re- 

 sembling in their structural details the adults from the intes- 

 tine. These young worms varied in length from 18 to 38 mm., and 

 if of the same species as the intestinal worms, as they appeared to be, 

 it is evident that the larvae of this species can develop much further 

 in the lungs than the larvae of Ascaris luinbrk-oides. 



Considering the migi-ation of the larvae of Ascaris and other in- 

 testinal nematodes through the lungs, it might be argued from an 

 evolutionary standpoint that parasitism of the lungs by nematodes 

 is a more primitive condition than parasitism of the alimentarj^ 

 tract, and that only as the worms acquired a complete immunity to 

 the effects of the digestive juices of the host did they move on into 

 the stomach or intestines. 



DETAILS OF EXPERIMENTS WITH ASCARIS. 



The following records of the writers' experiments do not cover 

 all the experiments that were made. A considerable number are 

 omitted, as they add little to what is shown by those selected, so 

 far as concerns the infection of experiment animals and the mi- 

 grations of the larvae in the body of the host. Numerous experi- 

 ments have also been made relating to the hatching of Ascaris eggs 

 in vitro, action of chemical reagents on the eggs, incubation of the 

 eggs, etc., but the details of these experiments will not be given in 

 the present bulletin. 



Experiment No. 1. 



January 15, 1917 : Seven white mice fed with bread liberally soaked with a 

 culture of eggs of Ascaris suum. 



January 19, 1917: Second feeding. 



January 24, 1917 : Third feeding. 



January 27, 1917 : Killed two of the mice, 12 days after the first feeding, 8 

 days after the second, 3 days after the third. Post-mortem examination showed 

 in one of the mice 21 larvae in one-half of the lungs, 1 larva in the small in- 

 testine, and 1 larva in the liver. In the other, 56 larvae in one-half of the 

 lungs, 1 larva in the esophagus, 2 larvse in the trachea, and none in the small 

 intestine. 



February 3, 1917: Two mice died, 19 days after the first feeding, 15 days 

 after the second, 10 days after the third. One was examined and 1 larva found 

 in the small intestine. The other mouse was not examined. Three of the 

 mice originally included in this experiment either escaped from the cage or 

 died and- were destroyed without post-mortem examination. The feces re- 

 maining in the cage at the close of the experiment were examined for larvge 

 but none were found. 



