THE CAUSE OF CHOLERA 89 



sick animals in the same pens; through infected water; by eating of 

 bacon trimmings^ and other waste meat products from hotels and 

 restaurants; by eating portions of dead carcasses which have been 

 carried into the feed lots by dogs or other means; by eating food 

 which has become infected by coming in contact with the boots or 

 shoes of those who have come from infected feed lots, such as 

 butchers, drovers, and hog buyers; or by mixing the germs with 

 other dead carcasses from the talons of buzzards and crows which 

 have come from a feast upon the dead body of hogs which have just 

 died from cholera. 



In a few cases the disease-producing material is probably car- 

 ried into the body of the well animal through the lungs ; that is, it 

 is breathed in with the air. In seasons when hog-cholera is prev- 

 alent the dust blown from cholera feed lots by whirlwinds and 

 sudden gusts of wind carries with it a considerable amount of 

 infectious material, and, without question, some few cases of 

 cholera are produced by the breathing in of this disease-laden dust. 

 Such cases usually show the most marked symptoms in the lungs 

 and throat, especially in the lungs. This is the class of cases 

 which show the most frequent complications of pneumonia and 

 which were formerly regarded as a separate disease — swine plague. 

 However, we may, and do, have cases with very severe changes in 

 the lungs which are not due to breathing in of infected dust. The 

 disease is not carried any great distance through the air, and hogs 

 can be kept as close as 10 feet to an infected herd with very little 

 danger of becoming infected if there is no direct communication 

 between the two feed lots, such as men going from one lot to the 

 other and carrying upon their shoes or boots the infected manure 

 from the lot containing the diseased animals. Birds, dogs, chick- 

 ens, pigeons, and other animals and birds are equally likely to carry 

 the infectious material, and if the hogs in the non-infected pen are 

 to be kept free from disease there must be no communication 

 whatever between the two pens. 



In cases where the width of a public road separates two hog 

 lots there is but little danger of transmission of the virus of cholera 

 from one herd to another, except through some of the means just 

 mentioned. Unfortunately, however, there is in practically all 

 such cases direct communication between the two feed lots. 



