GENERAL DISEASES. 63 



and sheep. The virus obtained from the vesicles and that 

 in the saliva and crusts is especially potent. Whether one 

 attack secures immunity against future ones or not is un- 

 certain. 



Symptoms. — Two or three days before the eruption deve- 

 lops, there may be mild fever and signs of impaired health, 

 but these preceding symptoms are in most cases unnotice- 

 able. The eruption commences as indurated red papules, 

 circular in shape, and shortly becoming depressed in their 

 central portions, and encircled by a bright red areola. In a 

 few days the papules become vesicular, and contain a clear 

 fluid which soon becomes more opaque. 



Lastly, a scab forms, which if accidentally detached, 

 discharges a limpid fluid, and leaves a depression, which 

 gradually fills by granulation. 



If the scab be not detached by force, healing by cicatriza- 

 tion, with little or no suppuration, will be accomplished in 

 fifteen to twenty days. 



During the period of eruption, and even after desiccation, 

 there is usually considerable swelling of the limbs and 

 inferior surface of the abdomen. 



The swelling may remain for several weeks after con- 

 valescence. 



Sometimes the pustules become confluent, and large 

 ulcerating surfaces are then produced, causing death of 

 large portions of the skin and subcutaneous tissue. 



Situation of Eruption. — The eruption is especially seen 

 on the extremities, from the knees and hocks to the feet. 

 The hind limbs especially are liable to be afl'ected, and often 

 swell. 



Other seats of eruption are the muzzle, lips, nostrils, 

 the mouth, sides of the tongue, and the nasal mucous 

 membrane. 



In these places the spots are smaller than those on the 



