Apr. 8, 1918 



Sources of Hog-Cholera Infection 



129 



Table XIII. — Results of tests to determine whether pigeons are disseminators of hog 



cho lera — Continued 



a Pigeons were shut out of pen 22 from November 29 to December 15 in order to give time for any infection 

 carried by them to develop in the exposed pigs. 



In these experiments three lots of pigs, each lot consisting of two 

 pigs, were exposed to possible infection from virus carried by pigeons, 

 at a distance of lo feet from a heavily infected pen. In the experiments 

 the periods of exposure were 30, 37, and 40 days, respectively, with 

 negative results in each case. In these tests the exposure of susceptible 

 pigs to possible infection from virus carried by pigeons was severe and 

 long continued. The pen which contained the sick pigs was not cleaned 

 during the course of the experiment and became very foul from the 

 excreta of the sick pigs; the pigeons were constantly passing from the 

 heavily infected pen to the pen containing the well pigs; and the distance 

 between the two pens was only 10 feet. Every opportunity was afforded, 

 therefore, for prolonged periods of time, for the pigeons to carry the 

 infection a very short distance. 



It goes without saying that these experiments do not prove that it is 

 impossible for pigeons to convey hog cholera. They do indicate, how- 

 ever, that the disease is probably not often carried in that way. 



EXPERIMENTS TO DETERMINE WHETHER RATS MAY HARBOR THE 

 VIRUS OF HOG CHOLERA 



In considering the various agencies which might be concerned in the 

 spread of hog cholera, the possibility suggested itself that rats which 

 had fed on the carcasses of cholera pigs might play a part in the spread 

 of the disease, and the following preliminary experiments were carried 

 out to test this point: 



Experiment XVII. — Two gray rats which were caught on the Station 

 premises were fed daily for five days with meat from the carcasses of 



