INFECTIOUS DISEASES 



273 



practicable for the production of hyperimmunizing virus in the near 

 future. 



Hog cholera virus is ultramicroscopie and passes through por- 



Fig. 69. Heart showing tissue hemorrhages due to hog cholera. B, 



Hyperemic areas. 



celain filters. The virus retains its virulence in fluids at room 

 temperature for from two to three months, but is destroyed by heat- 

 ing to seventy degrees Centigrade for one hour. When dried it be- 

 comes more resistant to the influence of high temperature. At the 



