CHAPTER XXVH. 



DISEASES OF THE SKIN. 



THE SCAB ERYSIPELATOTTS SCAB WILD FIRE AND IGNIS 



SACER OTHER CUTANEOUS ERUPTIONS SMALL POX, OR 



VARIOLA OVINA. 



THE SCAB. The scab is a cutaneous disease, analogous 

 to the mange in horses and the itch in men. It is caused and 

 propagated by a minute insect, the acarus. M. Walz, a 

 German veterinarian, who has thrown great light on the 

 habits of these parasites, says : 



"If one or more female acari are placed on the wool of a 

 sound sheep, they quickly travel to the root of it, and bury 

 themselves in the skin, the place at which they penetrated 

 being scarcely visible, or only distinguished by a minute red 

 point. On the tenth or twelfth day a little swelling may be 

 detected with the finger, and the skin changes its color, and 

 has a greenish blue tint. The pustule is now rapidly formed, 

 and about the sixteenth day breaks, and the mothers again 

 appear, with their little ones attached to their feet, and 

 covered by a portion of the shell of the egg from which they 

 have just escaped. These little ones immediately set to work 

 and penetrate the neighboring skin, and bury themselves 

 beneath it, and find their proper nourishment, and grow and 

 propagate, until the poor animal has myriads of them to prey 

 on him, and it is not wonderful that he should speedily sink. 

 Some of the male acari were placed on the sound skin of a 

 sheep, and they, too, burrowed their way and disappeared for 

 awhile, and the pustule in due time arose, but the itching 

 and the scab soon disappeared without the employment of 

 any remedy." 



The figures on the next page are copied from JVI. Walz's 

 work. 



The female acarus brings forth from eight to fifteen young 

 at a litter. 



