24 HOG CHOLEEA 



lachrymation often is pronounced. If death or 

 recovery does not take place in two or three days, 

 the tendency is for the disease to assume a chronic 

 type. One or more of the joints, usually the knee 

 or hock, becomes hot, painful, and swollen, render- 

 ing it difficult or impossible for the animal to 

 stand. In spite of this, the temperature falls and 

 is maintained close to normal, the appetite returns 

 and is surprisingly good considering the condition 

 of the animal and the fact that progressive ema- 

 ciation is taking place. Pneumonia sometimes 

 appears in these chronic cases, adding its train of 

 symptoms, but it fails to develop in a surprising 

 percentage -of cases, thus presenting a striking 

 comparison with field outbreaks formerly thought 

 to be caused solely by Bact. suisepticum, in 

 which pneumonia is the most constant manifesta- 

 tion. These facts lead us to doubt that the or- 

 ganism, acting alone, is the cause of a rapidly 

 transmissible disease in the field. 



Field observations are in almost perfect accord 

 with these experimental data. We have frequently 

 had outbreaks of "pure swine plague " reported 

 to us, and in those we have investigated, in which 

 there was evidence of transmissible disease, we 

 have without exception succeeded in positively 

 demonstrating or establishing the probable pres- 

 ence of the filterable hog cholera virus. It is also 

 significant that in the East, at least, cholera im- 



