LIFE HISTORY OF ASCARIS LUMBRICOIDES. 39 



May 7, 1 9] 7: FiJtli and last dose of Ascaris eggs given to the three remaining 

 pigs. 



June 4, 1917: Killed second pig 100 days since first iecdiuK witli Ascaris 

 eggs, 28 days since the last feeding. No Ascaris found. 



July 2, 1917: Killed third pig 128 days after first feeding with Ascaris 

 eggs, and 56 days after the last feeding. Six female Ascaris were found, 2.3 cm., 

 24 cm., 25 cm., 26 cm., 26.5 cm., and 27 cm. ; all in small intestine. 



July 7, 1917 : Killed fourth pig 133 days after the first feeding with Ascaris 

 eggs, and 61 days after the last. Eleven female Ascaris were found, measuring 



21 to 32 cm. 



PEN A PIGS NOT FED ASCARIS EGGS. 



•July 7, 1917 : Feces were again examined 167 days after the last fecal ex- 

 amination, when these pigs were first moved to their pi-esent quarters. The 

 combined feces showed a few Ascaris eggs. 



July 11, 1917 : Feces of first pig examined ; positive for Ascaris. 



July 12, 1917 : Feces of second pig examined ; positive for Ascaris. 



August 16. 1917 : Reexamination of feces of first pig ; Ascaris eggs present. 



August 17, 1917 : Reexamination of feces of second pig ; Ascaris eggs present. 



September 19. 1917 : Feces of both pigs examined ; Ascaris eggs present. 



February 7, 1918 : Feces of both pigs examined ; both positive for Ascaris. 



February 19, 1918 : Second pig passed one large female Ascaris following 

 dose of tartar emetic. 



February 20, 1918 : Both pigs killed. The first had 2 Ascaris, the second 

 (which had passed 1 Ascaris) had 1 remaining. 



Obviously the value of the conclusions to be derived from this experiment 

 is weakened by the fact that the check animals were also infested, in spite 

 of the precautions to guard against such a contingency. Considering the re- 

 hance which may be placed on a single dose of oil of chenopodium to rid 

 hogs of Ascaris (as shown by Hall and Foster, 1918) and the fact that 3 such 

 doses were given and the fecal examination following the last dose was nega- 

 tive, we have every reason to believe that the pigs were free from Ascaris 

 when placed in the clean pen. Nevertheless, we can not be certain that the 

 pigs were free from Ascaris, and they may have harbored young worms still 

 in course of migration. There is also to be considered the possibility of the 

 introduction of extraneous infection on the feet of the attendant or in tlie 

 feed. 



Considering first the experiment animals which were given but one feeding 

 of Ascaris eggs, we find that only one of the four animals became infested in 

 spite of the thousands of Ascaris eggs given to each pig, and this pig had 

 but 5 worms — not a very convincing proof of the direct life cycle of the pig 

 Ascaris. Furthermore, although the worms found were all about the same 

 length, indicating that they came from the same infection, they had reached 

 a rather large size, too large apparently for infection to have occurred only 



22 days before. 



Among the pigs which had received repeated doses of Ascaris eggs, 3 out 

 of 4 were infested, the heaviest infestation being 11 Ascaris, the lightest 2 

 Ascaris. It is impossible to decide whether or not the worms found in these 

 animals came from the eggs fed to them. Naturally, in view of the large 

 number of eggs fed, massive infestations would have been expected. This, 

 liowever, was not the case. A possible indication that the worms found 

 actually came from the eggs fed to the pigs in pen C is that the average size 

 of the worms from the pig killed 133 days after the first feeding and 61 



