40 BULLETIjST 817^ U. S. DEPT. OF AGRICULTURE. 



days after the last is greater than that of the worms from the pig killed 62 

 days after the first feeding and 15 days after the last. 



Experiment No. 19. 



Our failure in Experiment No. 18 to infect all the animals that were fed eggs, 

 and to get massive infestations, together with the fact that our check animals 

 became infested, led us to repeat the experiment. About this time the finding 

 of ascarids in the lung of a young pig, as already recorded (Ransom and Fos- 

 ter, 1917), and the fact that young animals have long been known to be par- 

 ticularly susceptible to parasitic infestation, suggested that more successful 

 results from infection experiments might be obtained if very young pigs were 

 used as subjects. 



With the idea of obtaining animals as young as (possible and to reduce the 

 chances of prior infection it was decided to take a pregnant sow, eliminate 

 all ascarids by treatment, place the sow in a clean pen for farrowing, and 

 feed the little pigs with Ascnris eggs as soon as they could be handled. 

 After numerous disappointments, a pregnant sow was procured, which, how- 

 ever, gave birth to 5 pigs before it could be examined and treated for Ascaris. 

 Two Aveeks after the birth of the pigs (of Avhich 2 only remained alive), the 

 feces of the sow were examined. One Ascaris egg was seen in the first exam- 

 ination and others in a subsequent examination. There was considerable 

 doubt after the first examination whether the single egg seen came from a 

 contamination of the fecal sample or indicated a slight infestation. At any 

 rate it was evident that if the sow was infested the little pigs had already 

 had an opportunity to pick" up eggs from the sow's feces, and it was therefore 

 decided not to disturb the sow by anthelmintic treatment, but to proceed 

 directly with the experiment on the pigs. 



September 22, 1917: Dosed one of the little pigs with culture of eggs of 

 Ascaris suum. Pig 15 days old when treated. 



September 29, 1917 : Pig died 7 days after dosing with Ascaris eggs. 

 October 1, 1917 : Post-mortem of pig. Ascaris larvse numerous in lungs, 

 trachea, and pharynx. None found in liver, spleen, esophagus, small or large 

 Intestine. Larvae from the trachea varied from 0.67 to 1.33 mm. in length, 

 0.03 to 0.06 mm. in width, with esophagus 0.12 to 0.21 mm. in length. 



October 4, 1917 : Fed second pig Avith 5 c. c. of a culture of eggs of Ascaris 

 suum. Pig now 27 days old. 

 October 16, 1917 : No signs of pneumonia. 

 November 10, 1917 : Second feeding of Ascaris eggs. 



November 17, 1917: Killed pig 44 days after the first feeding, 7 days after 

 the second. Liver and lungs both show numerous petechise similar to those 

 found in other experiment animals and associated with the invasion of these 

 organs by Ascaris larvfe. However, no larvae were seen in the preparations 

 examined. The small intestine contained S immature Ascaris, 3 of which 

 were accidentally cut by the enterotome. The remaining 5 measured as 

 follows : Length, 88 mm., 78 mm., 70 mm., 65 mm., and 60 mm. ; widtli, 1.5 

 ram., 1.3 mm., 1.2 mm., 1 mm., and 1 mm. 

 November 28, 1917 : Feces of sow examined ; several Ascaris eggs seen. 

 November .30, 1917: Sow killed; 7 Ascaris in small intestine, measuring 16 

 to 21 em. long. 



This experiment, like the preceding, is open to the criticism that outside 

 sources of infection were not excluded, since the pigs for the first month of life 

 were in intimate association with the mother which at the post-mortem was 

 proved to have been infested. This, liowever, has no bearing on the findings 



