PREPARATION OF ANTI-HOG-CHOLERA SERUM 95 



forced out follows the course of the vein or is dis- 

 tributed in adjacent tissues. 



Occasionally one encounters a fleshy-eared hog 

 exhibiting no ear vein which is visible to the naked 

 eye in ordinary light. Subjects of this kind may 

 usually be hypered by darkening the room and 

 holding an electric light bulb directly under the 

 ear. Small, deeply covered veins are thus ren- 

 dered plainly visible, and hypering is accom- 

 plished with surprising ease. 



Bangers and accidents due to hypering. The 

 ordinary immune hog will tolerate, without inci- 

 dent, intravenous injection of five mils of virus 

 per pound body weight. Usually there is no evi- 

 dence of pain or distress, and the animal lies 

 quietly while the dose is being administered. In 

 exceptional cases, however, sudden death occurs. 

 It is a curious fact that if distress is to appear, 

 it becomes evident before the first half of the dose 

 enters the circulation. Thus it is not quantity 

 alone that kills. Other factors may contribute, 

 but the principal one seems to be failure of nerv- 

 ous control over capillary contraction. The 

 capillary walls fail to adjust themselves to the 

 increased pressure, and as a consequence distend 

 and rupture. Usually the lungs alone bear evi- 

 dence of this fact, as they contain the first set of 

 capillaries through which the foreign blood must 



