Apr. 8, iti8 Sources of Hog Cholera Infection 127 



Two more pigs, No. 2317 and 2318, were injected with virus and placed 

 in pen 19 on September 30, to replace the two pigs which had died there 

 and to keep up the infection in this pen. Both of these pigs developed 

 cholera, No. 2317 dying on October 8 and No. 2318 on October 18. Both 

 animals showed extensive hemorrahgic lesions at autopsy. 



The two uninoculated pigs, No. 2285 and 2286, in clean pen 22 remained 

 perfectly well from September 18 to October 18, a period of 30 days, in 

 spite of the fact that during this time they were daily subjected to 

 possible infection from virus carried on the feet of the pigeons, which 

 divided their time between the pens, flying freely from side to side. In 

 order to test the susceptibility of pigs 2285 and 2286, and at the same 

 time prove that the virus of hog cholera was present in the litter of pen 

 19, these pigs, without being treated in any way, were transferred from 

 clean pen 22 to infected pen 19 on October 18. Both pigs picked up the 

 infection from the pen and developed typical hog cholera, pig 2286 dying 

 on November 6 and pig 2285 on November 17. At autopsy both pigs 

 revealed extensive hemorrhagic lesions and intestinal ulceration. It 

 was thus shown that the two pigs which were exposed to the pigeons for 

 30 days were susceptible pigs and that the virus of the hog cholera was 

 present in the litter of pen 19, but was not carried over by the pigeons. 



Experiment XV. — Two uninoculated, susceptible pigs, No, 2457 and 

 2458, were placed in clean pen 22, on October 20, for exposure to the 

 pigeons. During the period from October 20 to November 17, pen 19 

 was occupied by infected pigs (see Experiment XIV). Upon the death 

 of the last of these, on November 17, two more uninoculated, susceptible 

 pigs, No. 2766 and 2767, were placed in infected pen 19. These two 

 pigs, like their immediate predecessors, picked up the infection from 

 the pen, and developed typical hog cholera. Both died on November 

 27, showing extensive hemorrhagic lesions and intestinal ulceration. 



On November 29 the pigeons, which had alighted and fed in both 

 pens 19 and 22 continually since October 20, were shut off from pen 22. 

 They remained excluded until December 15, in order to give time for 

 any infection that had been carried by them to develop in the two 

 susceptible pigs, No. 2457 and 2458. These two pigs continued per- 

 fectly well throughout the entire period, although they had been exposed 

 to possible infection by the pigeons for 40 days, from October 20 to 

 November 29. 



On December 15, pigs 2457 and 2458, having failed to contract disease 

 from exposure to the pigeons, were transferred from pen 22 to pen 19, 

 and each injected with 5 c. c. of hog-cholera virus. This was done in 

 order to test the susceptibility of these pigs and to furnish fresh infec 

 tion to pen 19. Both pigs developed hog cholera following the virus 

 injection and both died on January 7, 1916, exhibiting extensive hemor- 

 rhagic lesions and intestinal ulceration at autopsy. 



