1 6 The Sheep- Scab. 



biting at the sores, or that adhere to the rubbing 

 places, are the frequent means of conveying the 

 parasites from sheep to sheep, and from the old 

 flock to the new; for these insects have a v^'^on- 

 derful vitality, enabling them to live for weeks 

 or even months, away from the source of their 

 nourishment and the field of their propagation. 

 So insinuating is this disease, and when once 

 established, so rapid is its diffusion, that, of the 

 sheep breeder owing an infected flock, one is led 

 to exclairn, with the poet Dryden, — 



" He sees the dird contagion spread so fast, 

 That where it seizes, all relief is vain." 



