86 REPORT OF THE BUREAU OP ANIMAL INDUSTRY. 



work, and scattered over the soil as slaked lime or as powder, used, in 

 short, wherever there is any suspicion of the presence of virus, may 

 reduce the time during which the ground should be kept unoccupied 

 to two weeks. It is our intention to make experiments on the disin- 

 fectant power of lime on pens and grounds, so that more definite 

 knowledge of its efficiency on a large scale may be obtained. 



It must be borne in mind that none of these precautions can take 

 the place of the isolation of the healthy upon fresh disinfected or 

 uninfected ground. No matter what may be the care taken in disin- 

 fection; if one sick animal, manufacturing and carrying virus about 

 within itself, so to speak, be allowed among healthy animals, the dis- 

 ease will spread nevertheless. 



The experience which has been gathered at the Experimental Sta- 

 tion during the past three years in the study of this disease has shown, 

 (1). That healthy pigs can be kept free from infection, even on a farm 

 where such diseas is constantly kept up for purposes of investiga- 

 tions, provided they are kept in clean pens and there is no transmis- 

 sion of virus from the sick to the well through implements of various 

 kinds, through the carelessness of farm hands carrying it on their 

 clothes, hands, shoes, etc.; (2). That the disease may be carried to a 

 previously uninfected locality by pigs bought from unknown sources; 

 (3). That the disease, supposed to be extinct, may lurk in a chronic 

 form in some animal without being recognised, aiid that this animal 

 may become the source of an acute outbreak among fresh animals, 

 usually in spring and fall when least expected; (4). That the safest 

 method of raising swine is to breed them on the place, either known 

 to be free from disease or thoroughly disinfected, and kept unoccu- 

 pied for half a year after an outbreak, and not to allow any commu- 

 nication with neighboring herds, nor to make any additions unless 

 the source be positively known to have been free from disease for at 

 least one year past. These rules will apply to swine plague so far as 

 our knowledge of the disease goes, with exceptions mentioned in the 

 article 011 that disease. 



INVESTIGATIONS ON THE ETIOLOGY OF INFECTIOUS PNEUMONIA 

 IN SWINE (SWINE PLAGUE). 



In the report for 1886 some -preliminary investigations were re- 

 corded concerning a disease in swine which differs from hog cholera, 

 not only in the character of the lesions which it presents, but also as 

 regards the organs attacked. The bacteria causing this disease are 

 quite different from those of hog cholera and readily distinguishable 

 by a number of tests. At the time of publication the material which 

 had been examined was not sufficient to warrant a detailed description, 

 nor were proofs adequate for complete demonstration. In February, 

 1887, an epizootic of this disease, which appeared in the District of 

 Columbia, was carefully studied, and a number of additional impor- 

 tant observations made in connection with the peculiar lesions which 

 it produces. 



The outbreak referred to appeared on a farm adjoining the Exper- 

 imental Station of the Bureau in February, 1887. The farm had 

 been free from swine diseases for several years. No clew could be 

 obtained of the manner in which the disease originated. In the 

 later stages of the outbreak the investigation was complicated by the 



