DISEASES OF SWINE AND OTHER ANIMALS. 17 



uutil it was again thawed, out, aud il' it was i)reserved for oue uight im- 

 cliauged in its potency, it would bo equally unaffected after the lajise of 

 many months, provided its liquids had remained in the same crystalline 

 condition throughout. It is in this way, no doubt, that the virus is often 

 preserved through the winter in pens and yards, as well as in cars and 

 other conveyances, to break out anew on returning spring. The imi)ort- 

 auce of this discovery, as apidied to preventive measures, cannot be over- 

 estimated. Infected yards and other open and uncovered places may 

 not be considered safe until after two months' vacation in summer, and 

 not then if sufficient rain has not fallen during the interval to insure the 

 soaking and putrid decomposition of all organic matter near the surface. 

 This will be made more apparent by reference to an experiment Avhich 

 resulted in the successful inoculation of pigs with virus that had been 

 kept for a month in dry wheat bran. In winter, on the other hand, the 

 yard or other open and infected i)lace may i)rove non-infecting for wrecks 

 aud even months and yet retain the virus in readiness for a new and 

 deadly course as soon as mild weather sets in. Safety under such cir- 

 cumstances is contingent on a disuse of the premises so long as the frost 

 continues, and for at least one month or more thereafter. Even during 

 the continuance of fi'ost such places are dangerous, as the heat of the 

 animal's body or of the rays of the sun at midday may suffice to set the 

 virus tree. 



Several of the examiners treat at length of hygienic and sanitary 

 measiu'es, and the attention of the reader is directed to their detailed re- 

 ports, which -Nvill be found below, without further comment. 

 2 sw 



